Too Hung up over Girl

Met this girl a while back. We've been getting on alright but I've started getting these paranoid feelings. Feelings like what if it doesn't work out. What if she suddenly meets someone else.

It's draining me. Haven't met someone I felt like this about in years. First time in 8 years in fact but I keep getting depressed thinking that something might go wrong or something. I shouldn't but I do.

We just dating at mo, not in a full relationship or anything.

I need to calm myself but can't. Anyone got any advice?