Frustrated with hcg

It has been nearly four weeks since my natural miscarriage and my doctor called last night to tell me that my hcg is still at 17 and that I need to go in AGAIN for more blood work. How long does it usually take to go back to normal? I'm just frustrated. Probably like a lot of you are. I was hoping I'd get lucky and ovulate two weeks after my mc and then get pregnant right away, but it's not looking like that's my path.