flucloxacillin

I am currently taking  flucloxacillin  4 times a day and I'm literally only on my second tablet and have never felt so bad on antibiotics??? Has anyone experienced this. I feel so sick and quite short of breath. Finding it hard to stand. After the first dose i fell asleep for a couple hours too. 
I mean I'm also on some other medication but I've taken a weaker version of it before many many times and I don't think it's that. Just becaus of my experience with it before. 
Anyway, is what I'm experiencing with flucloxacillin normal? My doctors surgery is closed rn so cannot phone