I'm with disneyprincess 87- Always trust your gut.
If your gut tells you there's more to it with an ex, give it up as a bad job. Don't allow yourself to fall into the deepest, darkest pits of hell with insecurity, paranoia, suspicion.
If anybody close to him warns you, about him, even subtely, give it up. My exes best friend and Uncle cared about me enough to give me a heads up. I chose to ignore it.
Don't ignore any flags. When we are in love, we often choose to bury our head in the sand, unwilling to see waht is right in front of us. Over time, the more red flags come up or continue, the harder it is to ignire them. In my experience, this level of inner conflict can, at times, make you feel as though you are genuinely cracking up. No man is worth your peace of mind, give it up.
If his morals are too different to yours, either agree to disagree or give it up. Agreeing to disagree is unlikely to work in the long run though, as these same morals and belief systems will be considered by both when making larger decisions surrounding parenting, housing, employment, finances etc.
If he is shit with money, give it up. This will not change and will cause you ridiculous amounts of stress and you will have a future that includes nothing better than you have now- if anything it will get worse over time due to decreased earning potential.
If he indulges in any activity excessivelly, get rid. My ex was a gamer and a habitual stoner. He worked part time, when he wasn't working, he wanted to game and get stoned.
Drugs- stay away from addicts. No amount of love or compassion will change their addiction. Many believe that Cannabis is not much of an issue these days, and I honestly believe the odd tote at night or the weekend is not much of an issue. My ex smoked from the moment he got up at 6am, until he went to bed. When he did not have his weed, he became irritable and more aggressive than usual. If we went on a holiday, he would have to buy a weeks worth in advance to take along with us. One caravan holiday, the caravans were so close together and the class of people on the park prevented him from being able to smoke it on the decking. He was a fucking arse all week and ruined it for everyone. Also money, a habit is aexpensive, even if he claimed it was not a habit. They claim this, don't fall for it get out.
Any hint of a temper that scares you, makes you anxious, get out.
If it doesn't feel like he's joking, he's not.
If you are becoming insecure, whre before you were not, it's him, not you, get out. This can also be the case even though you've been cheated on in the past.
I could go on forever.
Become comfortable with your own company, become financially independent. Build a life for yourself that you like, or preferably love. Once this is achieved, you are less likely to twist yourself up in knots for a man that doesn't deserve you.