Low HCG levels and only 20% rise

I am 4wks 6days today. Had very light spotting on Friday. EPU took bloods and my HCG levels were only 18. Repeated today and they'd only increased by 20% to 22. Got to back again in 48 hrs. Other symptoms still very present eg sore boobs and feeling nauseous. Now very anxious and deflated. Had a mc earlier this year and it's taken six months to conceive again. Has anyone had anything similar and gone on to have a successful pregnancy? Any ray of hope right now would be gratefully received.