Losing weight early pregnancy

I weighed in at 122lbs at my 7 wk apt and had another apt the next week at 124lbs but went to my primary care dr yesterday for a rash on my hands (possible MRSA) and weighed 120lbs. I'm trying not to freak out about the MRSA and I have only lost 4 lbs, but I still hoped to have a steady incline. Should I be worried?