My toxic friendships are stressing me out?

So I have friends who have been distant. I'm wondering if it's worth continuing trying to pursue a friendship that seems one sided. We've had our ups and downs, lots of friendship break ups and drama. The longest I wasn't friends with them for is 4 years. I contacted one of them 3 years ago telling her how much she hurt me and it was a mistake because she was nasty to me. Last April I got back in touch with them and we are friends again, but it hasn't been perfect. I feel like we've grown apart since I was 20 and they were 22 when we stopped being friends; now we are 25 and 27. I feel like I'm trying to make up time with them and they seem like they aren't interested because they had time when they were younger to go out, be silly etc.

I also feel like they are their own clique and that I'm an outsider. They stick up for each other and never take my side. A few months ago we had a fight that resulted in them both de-friending me off Facebook for no reason. They blamed me for the fight. They got upset with me because I was not responding to them because I was with my ex boyfriend at a family party his family was having and it turned into a fight. What triggered one of them was my comment about her bf (who was her sex buddy at the time this occurred) hitting on me while we were all drunk, on Snapchat. She clearly was still upset even though I apologized. Well she started saying nasty things to me and contacting non stop being a jerk. I have no idea why they even picked a fight in general since they never respond when I contact them so they had no right to be upset because I was busy and not responding to them. Most of the time they just "read" my messages and I kept clicking out of the messages they were sending me when I was at the party.

The whole friendship has been on my mind everyday. It stresses me out because I have no idea what's going on. They tell me everything is fine but their actions don't reflect that. They never contact me, rarely ask to me. I'm not sure what else I can do, but this seems toxic. I also try to be understanding of the fact that one of them has bipolar and depression and the other may have aspergers like I do.