1st trimester symptoms.

Ta
I am 5 weeks and one day today. I used to work out four times a week and always said I would stay active when I get pregnant. All I want to do is eat sleep and repeat. I have energy and feel weak. I tried so exercises today on my yoga mat and my legs just felt week. I'm a first time mom so I'm all like wow is it too early to feel this way? 
I also took a five week picture yesterday for my first belly picture. Of course it's all bloat right now but you can see that something is going on. I feel so fat. My husband said my boobs are already bigger. My face and arms even look fatter. I'm thinking what?????? Your not supposed to put weight on that fast. 
So today I'm trying to be more active. But I don't want to over due anything because I want to keep my baby safe. Does anyone have any advice for me please?