breastfeeding strike...

Melissa
Hello, 
My 4month old has always been an amazing breastfeeder I've never had any problems until this week he is totally uninterested in me, apart from first thing in the morning and if he wakes in the night. 
I try to put him on and be sucks for a moment or two then gets so upset and pulls away, I know he's hungry and so have given him bottles with half my milk , half formula. I don't know whether to just give up but the guilt of giving up makes me so sad and I'm worried my happy little content boys going to change, he's never been much of a crier until now, which I figured was probably teething but I feel a bit unwanted by him! :( 
Anyone got any advice I'm a 1st time mummy too!! X