just nervous

I'm 4 +4 today and I'm starting to have some mild cramping and pulling on my lower left side. I'm freaking out because I had a missed miscarriage in February and a chemical pregnancy in May. It's not really painful more of a discomfort but the pulling cramping feeling is really worrying me. I just want this pregnancy to stick. all i have been doing since I found out is worry. I went Monday and got blood work HCG was 144 and Wednesday it was 307 so it's doubling but I'm still so worried I go back Monday for another hCG but I don't have a ultrasound until August 7th when I'll be 7 weeks. just don't know what this feeling is if it's normal or something to worry about.