stress out mum

My baby is 2 weeks old and just started formula. I am giving him mix of formula and breastmilk but he seem to prefer formula instead of breastmilk. He seem to fight when i try to latch him on my breast.i try to stay as calm as possible. Both breast have milk because they are always leaking and sometimes it spray out the milk without me disturbing them. I do try to collect in the hakka breastpump.i now have regrets that i gave him formula because before he do not have any problem on lactching on. What should i do?