I think you need to stop compromising and take back your power.
First, saying no is not a bad thing, and you already know what saying yes and being agreeable has gotten you, so start telling people no.
I think setting boundaries and guiding rules for yourself might also help.
Try making a list of things you are willing to tolerate from people (for most, this will be short to nonexistent) and a list of things you are not willing to tolerate.
Then start building from there, living by your own code and standards.
Someone asks you to go to a game. No thanks.
Someone asked you to cover all of your friends' pints. No
Someone shows up at your door unannounced, and you don't want to deal with them right then. You tell them it has to be at another time.
You have friends who always call, and it is not a crisis. You will get back to them later. (Take note: If there is a crisis, death, breakdown, etc., try to handle it accordingly.)
When someone violates any of your guiding principles, you stand up for yourself and address the situation calmly. If the boundaries you set are not respected again, you either address it again or cut ties.
Also, don't keep people around you who don't respect you or your boundaries out of fear of being alone.
Sorry for the long ramble