Help please!

My beautiful 10 weeks old girl has suddenly changed from a very content, happy, smiling baby to a very grumpy one. For the last 3-4 days she rarely smiles, cries whenever I put her down and just really doesn't seem herself. She eat well, lots of wet nappies, poos once sometimes twice a day, sleeps well at night (between 8-9 hours), naps well in a day too. Went to the doctors few days ago, she's not teething, doesn't have a thrush and seems healthy but she really isn't herself! She has been bringing back lots of the formula after a fed but that's all. And also I've noticed that in the morning her feet are quite sweaty although she's doesn't seem at all hot. I don't want to take her to the doctors and seem like a crazy person but she really isn't herself!!! She's my first so I can't compare it to anyone. Is it just a phase? Or a growth spurt? Please I need some advice! I'm worried sick