Sorry to hear about your situation.

Allah is not angry with you. You sound like you are sincere and have a good heart, and these are the things that are important. Sometimes these thoughts pop up by themselves, or sometimes they are from shayateen. The best thing to do is just let the thoughts come and go on their own and remember that Allah does not blame us for things that are outside our control. Sometimes when we try not to think something, we end up thinking about it more. Also just do the salat as best as you can. You could also see if praying in a different location (like mosque, workplace, park, friend's house, etc) helps.

If you have some specific reason why you are upset with Allah (for instance, some people are upset when they lose a job, divorce, etc., as they blame Allah), this is something that is good to work through personally and spend some time sitting with Allah and doing dua or contemplating about to make peace about. 

We have lots of ups and downs in our religious life, inshallah you will get through this too.