Exercising while pregnant

I'm so nervous to excersise...or really do anything while pregnant. I'm 4 weeks and suffered a miscarriage in January. Before becoming pregnant, I was very active at our gym and went 6-7 days a week. I'm craving the gym. I want to workout so bad but I'm so incredibly scared of harming my pregnancy. Any advice from any other expecting moms who excercise during their pregnancy? Specifically excersiging in the first trimester?