The beginning of a relationship is always awkward. It's a feeling out process. Sure, it'd be nice to skip ahead to the good part where you can just cuddle, eat pizza and watch Netflix, but you need to work your way up to that.
This is a perfect example of moving on from the past. It's sad it had to end, but it ended for a reason. Learn from your mistakes so they don't repeat in your next relationship. While your feelings may be hurt, that person helped you grow and helped you ultimately find someone you'll be happier with.
Communication is vital in making your relationship work. If you're only trying to explain your own emotions, you won't understand theirs. Listen to what's going on with them. You'll save each other a lot of grief in the long run.
Sometimes when you've been with someone for so long everything feels comfortable and easy. But just because they're here now doesn't mean they'll always be here. Give them a reason to stay, and tell them how much you appreciate them for who they are and what they do.
Being a partner to someone means being there when times are good, but also when times are rough. You should be able to help them back up, and not judge them for falling down. You'll want someone to do the same for you some day.
We all have things we've done that we regret. Who you were yesterday isn't who you are today. Let your partner know of your past, and if you're trying to change. Let them help you, if need be. But only change for you, not for them.
If you're not happy, bringing someone else on board won't solve your problems, it'll compound them. Be happy with yourself, then you can be happy with someone else who'll love you for you. No matter how weird you may be. Hey, we all have our own weird things we do in relationships.