You just described my last relationship to a tee. We were together for a long time, and it actually took me 2 years to break up with him because he would guilt trip me and I just couldn't do it. The whole relationship was pretty much based on me feeling guilty for not loving him enough and staying withvhim because I felt bad for him. I finally took charge of my life and broke up with him over the phone–I knew if it was in person, he would say something or start crying and I wouldn't be able to go through with it.
You have to make a decision and then be firm with it. Make a contract with yourself: say “No, I can't do that.” No matter how much he pleads, you do not say “well maybe we can try…” or anything except “No”. Even if it may not be nefariously, these guys have been emotionally blackmailing us for so long that they know exactly what to say to make you act the way they want.
It took me close to a year before I could start dating again and until I fully realized that not staying with him was the best thing I ever did. I met an amazing guy who made me feel so much love and passion, I didn't even know it could be this way outside of the movies. He made me realize how insane it is to be expected to sacrifice yourself for someone else. The above poster is absolutely correct: we are not their mothers, we are equal partners and we deserve to have our happiness just as much as they do.
One word of advice for when you find someone that you want to start dating again: be completely honest 100% with him. I think what happens a lot of times is that you're afraid to say things that you think will disappoint them or hurt them, so you keep it all inside and say things are fine. As a result, you feel distant and frustrated. On our third date, I told him everything about my past relationship and was completely honest with him. The best surprise? He had issues too from his last relationships, and we talked about everything and got it all into the open where they're not uncomfortable secrets anymore. He was really grateful that I was being honest with him. No matter what relationship you're in, honesty and communication is the most important thing you can do to keep that happiness.