Son 2 yr old says mouth hurts and woke screaming. Has white maybe blisters back throat tonsils. 103 104 fever. Doc said mayb hfmouth, strepor whatelse?

Viral vs bacterial. This could be many things. Strep throat causes fever headache and sore throat often with what is called exudate. Mono can have similar symptoms as well. Viral illnesses usually cause blisters that are whitish centrally with surrounding erythema, ie redness. Very important to make sure your child is able to drink well and swallow, if not your child should be seen asap.
Herpangina. Among the most painful of sore throats, with little blisters over just the tonsillar pillars. My best guess. It's not treatable except with topical anesthetics and it resolves by itself.
Mono. Could also be mono (epstein barr virus). For his age and the way you describe it hand, foot and mouth would be the most likely. Herpes simplex virus 1 also causes sores in the mouth and fever. The herpes virus sores tend to be more in the front of the mouth, but not always. I am assuming he is vaccinated.