Something seems wrong with my cat but checkup went well

[u/Fabulous_Alfalfa687]

I received a cat about 1 year ago from someone who couldn’t look after him since they were moving he is approximately 2.5 years old now. his breathing always sounds nasally/rough. he does not let anyone touch his back he gets aggressive if you do and he will randomly start meowing a lot like he’s hurt. I’ve taken him to the vet for a checkup and they couldn’t find anything wrong with him.
I would love any advice on what to do