Need advice desperately

This is very very complicated and a little long but I really need advice. My ex boyfriend passed away 2 1/2 months ago and shortly after he passed away I was spending a lot of time with his best friend, who I became very close with and had previously hooked up with at a party. We eventually ended up having sex and still talk, and I really like him and enjoy spending time with him however my some of friends kinda shit on my dreams. There always telling me "oh you can do better" but I don't want anyone else and I just want to spend time with him and they don't seem to get that. I know he's not perfect but he treats me like a princess and a few of my friends are very supportive of us talking however some of them are very very rude to me about it. He takes care of me and regularly checks up on how I'm doing and how I'm feeling emotionally. I really don't know what to do about my friends because he makes me happy and I don't understand why they can't accept that. Everyone else has but them. I'm not sure how to approach them or anything especially when they make dumb mistakes with guys and I don't and I support them but they won't support me. Any ideas what I should do? And is it horrible of us to be happy together because he was my exs best friend?