Concise answers first!
Yes, you certainly can! Nobody can really determine this but you, though. Identity is a personal thing. But having been married nor having children nor even being in romantic love precludes you from the aromanticism or the aro spectrum.
Maybe! It's difficult re-analyzing your past through your current perspective, but again, this is something only you can decide, since it's your life and your identity and your experiences.
Longer answers, if you want some aro and identity-based analysis.
Identity is complicated and weird. This is because it's personal and completely subjective. You can't take any test and have it spit out the "correct" identity for you. There is no such thing as labeling yourself incorrectly, imo, only outgrowing a label or exploring labels and deciding they're not longer right for you. Howe we label should be based on what label we want to use, what label comforts us, what label feels most right to us, what label helps us best communicate with others how we feel, and/or what label best connects us with a community who has had similar experiences to us/that we can personally connect with/understand. How we label can be determined by whichever of those is most important to us at the time. But how we label is also totally determined by: our exposure to and knowledge of certain labels, not to mention it can be impacted by our overall headspace, place in life, who're we're around socially, etc. And we don't always have a clear understanding of what draws us to one label over another. It's like... you may crave spaghetti and eat it for a week straight and then the next week find spaghetti unappealing even though you like it perfectly fine and always have. Or it's like starting a new TV show but not having the headspace to take in new content and end up not liking the show, even though you try it again six months later and fall in love with the show. Our emotions and feelings are so subjective and impacted by so many little things and big things, and this can impact how we feel even about our own identity on a small scale and certainly in the long-term.
When I was 21 - 22, I started questioning my gender for the first time in my life. Around 23, even though completely unsure and doubtful and not feeling valid enough, I decided to label as nonbinary. At around 25, I finally came to terms with being nonbinary and was completely comfortable identifying that way. Then at 26, I realized I also identified as genderqueer. For a while, I thought my gender, like my romantic attraction, was impacted by the abusive relationship I had recently escaped at the time of my questioning. In the following years, I know for sure the relationship did impact my romantic attraction (as well as me becoming aplatonic), but I've started to realize that the same probably isn't true for my gender. Looking back, I can now see several signs that could have pointed to me being nonbinary when I was younger and just not having the language for it or a big enough reason to cause me to really think about it enough to realize it. But in the end... I'll really never know if I was really nonbinary when I was younger or not because our identities? They're also largely impacted by our perspective and understanding of ourselves.
We are continually discovering more about ourselves as we grow and understanding ourselves and our desires in different ways. We also experience more and what we experience can impact us, who we are, and who we understand we are, changing our understanding of our identity or making a certain aspect of our identity more or less important to us (in recent times, my aromanticism has become a bigger part of my experience than my asexuality, which was previously a much bigger component of who I was than my romantic attraction), or giving us new understanding of how we feel and what we want, making different labels seem more appealing/more accurate to us.
So regarding your past. Maybe you were aromantic with an exception. Maybe you were a little more gray-aromantic and now you're less gray due to time and experiences and even natural fluctuations that could have happened with your aromanticism. Maybe you were in love but it was more queerplatonic or platonic than it was romantic, but a romantic relationship was something you desired and felt fulfilling to you.
Whatever it was, whether past or present you feels aromantic is a good application for your past self or not, you are valid! It is valid to use a different label when you feel that different label suits you. It is valid to ID in different ways over the course of your life. It is valid to feel aromantic fits you now even if it didn't in the past. It is valid to not know if aromantic fit you in your past or not. You are valid.
Identity is weird and confusing and complicated. It's never simple, even when it feels simple - or maybe it is simple sometimes but that doesn't mean it will always feel simple to you throughout your whole life. People are never clear cut. We're complex. We're enigmatic. We're walking contradictions, and that's okay. Labels aren't some inherent part of our existence. We create labels because we think deeply and like we patterns and linear understanding and sorting things into easier-to-understand boxes makes it easier for us to navigate the beautiful mess that humanity and the world at large is.
I'm really glad you've found the label aromantic and that it's providing comfort to you! That's what labels should do for us. < 3
Hope this made sense and was helpful!