My son is scared of using the toilet or potty HELP!?

My son is 2 and a half and is so scared of the toilet and a potty. We tried him with a new toilet seat and he screams and shakes when hes on it. I take him 2 the toilet with me and show him there's nothing to be scared about but he still wont go. I bought him a normal potty and he wont use that and ive just bought him a car potty with a lift up seat. He sits on it with seat down but not up. Tonight I tried him running around without a nappy which i do often and tried to catch the pee in a container and he just stopped peeing cried and ran off. I then sat him down and tilted the bowl towards him to catch it and gave him juice and read a story, He then cried and cried so i let him up and he peed i went 2 catch it and he stopped and cried again. He also has Speech problems and cannot talk apart from mama baba Nana ETC. I didn't understand why hes so scared. he goes from calm to petrified in 2 seconds. He doesn't just cry he physical shakes and cried like hes being hurt. Any ideas please i have no idea what to do ??