I believe what the previous poster said is dead on spot with what I was thinking. I've been with the same person for 5 years and it's not an easy task. I've learned what the pp said throughout the years.
I've been where you are only my man, at the time, was a complete total ***** face. Nevertheless, I was so anxious and depressed about us possibility breaking up.

I know the fear of being alone but we have to find a place within us to be comfortable with ourselves. It's hard to renew your mind like that but it's worth it.

One thing I find very important is to not allow your happiness to come solely from our partner. Why? Because 5years, 10years, 20years together. It doesn't matter. A relationship is constant changing for each other and ourselves. It's constant compromise, forgiveness and loyalty.

You have been with him 4months. I'lI promise you that things won't stay perky forever and if you love him the way you do, you need to find it within yourself to rationally handle those tough times.

A wise old man once told me if you go into anything thinking you will fail, you most likely will.
This is because we become the thoughts we feed the most. (Depression/mania because we tend to have a harder time controlling our thoughts.)

Focus on the positive as much as you can and enjoy your time together.