Am I wrong?

Hello ladies! I've been in a relationship for about 2 years. Great guy. Extremely sweet. However, lately things are starting to take a turn and I'm not sure how to feel. He is constantly bailing on important promises, and plans, being rude and disrespectful, then come to find out he's been talking to his guy friends about other women. Don't get me wrong. It happens I understand. But reading about how he wants to pleasure other woman and how they made him feel when they were seeing eachother. Makes me feel betrayed and disgusted. Am I wrong? We have had some problems with girls in the past. This was just the recent. I love sex as much as the next girl but I mean. It makes me feel bad to think that it is starting to take over my relationship. And me not always wanting to talk about or have sex  leads to attitude and arguing. Now I have gotten advice from a "friend" She basically told me he's a man so it's okay he has needs and me as his girlfriend I need to fulfill them. Also I was told that I was selfish, I don't respect him, and I can't handle the truth he has for me, also that if I couldn't do my part as a gf I needed to opt out. At this point I'm lost on what to do. I don't want to throw away 2 years but I've never felt so lost. Any advice?