Hey there 
I know it's something that's easier said than done but please don't beat yourself up.
You said you had a termination at 15 & your boyfriend was abusive, don't feel guilty for making the decision that was best for you at that time. That doesn't make you a bad person at all. It's a choice so many women (more than a lot of people think) have had to make, for some it's an easy decision and not thought about again (which is fine as they know what is best for their life) but for others it can be something that stays for a long time, but it doesn't mean you should beat yourself up about it as you didn't do anything wrong.
you can't change what happened and sometimes your mind will over run and dwell on things you really don't want it to but please remind yourself that you are a strong person, things don't always happen the way we want them to but that doesn't make us anything other than human. Don't blame yourself you was a teen and you deserved better than the situation you was in.
I noticed you said that you was addicted to drugs so it's an addiction you have overcome? That's something to be proud of and a reminder of your strength!
I think when there are mental health issues involved such as depression, bipolar or anxiety it's such an easy trap to fall into of reflecting on our guilt, things we wish were different & punishing ourself for these things, because that's what the depression/anxiety wants us to feel but it doesn't mean that it's right and we should feel like that. Might be worth speaking to your GP to see if they can advise anything for you to help you feeling like this?
I think that with everything going on right now with the virus & lockdown (if you're in Uk) that being home or having so much time on our hands our minds go on overdrive, especially as we can't really visit anyone properly, or have visitors in the house or go out for leisurely activities and it's really awful but please don't feel alone 
It's not easy to just say to yourself "stop dwelling on the past and move forward!" Our minds don't work like that (would be lovely if they did lol). This is something that takes time with a lot of self encouragement & support.
Keep on focusing on the good things going, your good qualities & things that make you happy no matter how big or small. You can't change things in your past but you can make a better future for yourself - please don't continue to punish yourself as we are all only human & things do not always go down the routes we want them too x
Sorry this is a bit of a lengthy reply. I really hope you're feeling better x