This is an awkward place to be in a relationship, and I'm sorry to hear you're feeling stuck here. After 5 years the strength of your relationship should be fairly obvious; by now you should be able to trust that if your boyfriend ran into his ex, he's handle it maturely and without incident. Talk to your boyfriend about this; tell him you need reassurance. Then decide for yourself whether you can trust what he has to say.
Listen to your instincts. If you sense he's not over her, then it's up to you whether to stay with someone who isn't loving you as you deserve, or strike out on your own and find that relationship where you will feel cherished and reassured. Ultimately the person whose responsible for your happiness is you, so take charge!
He was with this girl for 4 years. He left her to be with you. He's now been with you for 5 years, and he wants to marry you. Those facts definitely suggest it's you he loves, not her, or anyone else.
I understand your difficulties coming to terms with his previous relationships. It is difficult, when you have only ever loved one person, to understand how someone else could have loved someone different then left them and just left that all behind. My wife is the only person I've had a relationship with, but she'd had a few lightweight flings before we met and I know that I obsessed over them for a while, they were hard for me to deal with. You just have to know and trust that you are the one he wants, and if he wants to marry you that's a pretty good indication.
I agree with S Healer - you should trust your instinct. Instinct is our 'biological alarm'. It can tell you what you can't see. Good luck
Thank you, for the time you shared... I learned something from it. Please allow me to add this conversation... In our 5 yrs we shared a lot and even fought a lot. We had this huge difference in our likes and what we stand in life. (probably because we had this age gap... Is it really?) He is not sweet and romantic to me,he even get easily angry with me (which made me ask if he did this to his ex gfs) especially whenever I tease him. He also smoke when I am not around (which leads to our fight) and drink alcohol for about 8 times drunk a month...But I love him and I started to hate it with his vices... I know he cares to me in some other way... BUT still he is not that Romantic and Sweet. I just want to clear some questions in my mind. Thanks again, now am able to express whats inside of me.
It sounds that you need something from the relationship in which is not giving you and those are things to consider. The most important content in a relationship is the fact of feeling of being loved by someone, being able to trust that someone and being able to rely on that person. I was in a similiar relationship years ago, and after I left him, I learned what a relationship really is. I am now married and two years later we laugh and play everyday, in spit of some hardships we have faced. Don't short change yourself, trust your instincts and yourself,... he is supposed to be there to make you feel happy about yourself, to make you feel safe and wanted..... not the other way around. good luck....