need advice! why am I feeling like this...

Sarah • Mother to George Owen 21/3/18 💙 Pregnant with Baby Owen #2 29/10/19 💙
I'm having pains in my stomach, my boobs are swollen & heavy, feeling slightly nauseous & now I feel achy like as if I have the flu coming. 
Glow says I'm only 3 DPO so I know I wouldn't have pregnancy symptoms so why am I feeling like this. 
Anyone have any ideas or can give me some advice as to why I feel like this?