Always Paranoid

I need some advice. I've been married to my husband for about 5 months now. He's in the military so he's frequently gone. We got together before he joined. Anyways. Ever since we got married, I've been extremely jealous and just always worried that he's going to leave me or cheat on me. I wasn't like this before...I was so nonchalant with him...and now I'm just constantly worrying. I'm always stressed out about it. Every day. I don't know what to do.