Sorry in advance for the long explanation, I just want everyone to be on the same page as me.

My most current ex-girlfriend and I broke up about 2 years ago (after dating for more than 2 years), but we've had a very complicated relationship since then, up until a few months ago when we finally stopped talking to one another. Since then, she had gotten a boyfriend. By some completely random occurrence, we started talking again, but strictly just as friends. I could tell that was only friendly talk because she would talk about her life and her boyfriend to me, both the good and the bad, and nothing suggestive of me and her; it was talk just as friends. I went along with it because she and I have always been really good at conversation. She had very recently told me how her boyfriend and her were having problems, but then they had a deep conversation about it and in the end it brought them so much closer together, and at that point I not only realized how lonely I've been feeling lately, but how much I miss being in a relationship. I know I'm feeling this because of the fact that I'm talking to her, but I'm wondering if I should continue talking to her just to be a good friend (because she's really in short supply of those), or if I should be up front with her and tell her that talking to her is doing me more harm than good, and just end it... I don't know which I should do.

You're no longer together. You need to consider your feelings first and foremost.

My advice? Go NO-contact.

I agree completely, if you are in a relationship, you have to take the other person's feelings into account. Since you're not together, you need to look out for numero uno. It sounds selfish, but if you try to worry about everyone else, you'll just make yourself miserable.

Don't stress yourself out talking to her. If you really are feeling that it's too hard on you, then you do need to speak up and end it now before you get too emotionally involved.

I agree with the other posters. You are setting yourself up for MORE pain.

You answered your own question "or if I should be up front with her and tell her that talking to her is doing me more harm than good, and just end it"
If its doing more harm then good, then its obvious what you have to do. Let her enjoy her relationship, you need to get on with your life.

You will find a girl that you can open up to, and you won't feel lonely when you guys hit if off.

Contacting your ex makes you feel well for a very short period! My advice for you is to go no contact ( wtever your feelings r ) and don't bother yourself thinking of her. Your helping her on your own expense, your hurting yourself for what? Just to be a good friend? Ur only talking with her about her boyfriend , does this make you happy or feel good ? NEVER!! Move on , give yourself a little time and then u'll be ready for another relationship . But now your putting yourself in a pause mode, nth else!