I don't know if I have just got simply fat but I haven't missed a period just had them irregular and also no clothes are fitting me the same anymore and I have been feeling tired and mood a lot,I already have a 3 year old and feel like I am pregnant again but I have taken 2 tests and both negative, could I be pregnant or just fat?

Yes it could be either, or some other medical condition. There is just not enough info or way to tell over the internet.

It sounds like time for a doctor visit