Misleading symptoms

Hi, i'm 7 weeks pregnant & wasn't sure if i should be expecting any major symptoms. Apart from feeling fatique, backpain, tightness, nausea w/o vomiting & thirsty (thou i drank lotsa of water). My tender breast suddenly subsiding, same goes with the hot flush that i'm feeling. Cramp between thighs & calfs are gone too. Feeling just a mild cramp in tummy. Did my scanning last monday & i saw the heartbeat. Was suppose to expect two since my hcg was very high. But im fortunate enough to have one survive. Still, there's high chance of miscarriage which i'm really worried about. Anyone experience this before?