I have been where you are.
One thing that helped me was a gradual understanding that I was the needy person and I was using other people to try and fill a hole that they had no chance of filling. Learning to meet my own needs, find and except healthy support from others in doing so has been life changing.
Understanding that whilst I have certainly been “taken advantage of” many times, it was often due to my lack of boundaries and inability to prioritize my needs.
Now the problem is always that it is circular. You don’t feel worthy of having your needs met so you don’t ask for anything or set boundaries. But because your needs are not met and people cross your boundaries, your self worth decreases.
The trick is to start acting like you have self worth even if you don’t feel it. Identify areas where your boundaries are weak and start saying no. It will feel TERRIBLE but you just have to sit with that feeling and soothe your way through it, speak to yourself as you would a small child (in fact it’s very useful to conceptualize à part of you as a small child who deserves love and comfort - it’s easier than trying to soothe the adult self who we often think should have it together). There’s no quick fix and old patterns will want to reassert themselves but the only way is to keep plugging at it.
Do you know where these patterns come from and have you had any therapy? I sort of self therapied myself with the help of some online courses, YouTube vids and a few sessions with a healer friend - it’s an ongoing process but you can do it.
As for other people? You are not helping anybody if your actions are hurting you. All you will be engaging in is co-dependant enabling of destructive patterns, always, especially when your “help” is coming from a place of need in yourself. They are better to be left to sort their own shit out, it’s far more effective and empowering anyway.
Good luck 