I am beside myself

I had Molly weighed today by my MCHN and in the last 4 weeks not only has she not gained any thing she has lost 48g. At 8 wks she was 4.050kg and today she was 4.002. I am so scared the MCHN was talking about failure to thrive. I have to take the fenugreed daily and take her in next week again and if no improvement investigations will start. Everyone around me is telling me this is why she is unsettled however after starting with the infacol last night today she has been a star. I am been told left right and centre to FF her. I just dont know what to do. I really want to continue to BF and yet feel like i am failing her and its my fault that her weight gain is so minimal. I blame myself for not weighing her in the last 4 weeks. DH thinks i am overreacting and has told me its one weigh in and not to stress. I wouldnt stress if it was only a week with no gain but for weeks no gain with a loss is scaring the ***** out of me.