Stubborn kid

My almost 4 year old who is fully capable of putting and taking off his clothes refuses to do so. He is so stubborn. He is allowed to pick out his clothes and pajamas we've tried giving him options it doesn't matter he won't do it. Every evening its a fight to get him in a pullup for bed he's still needing them and pajamas is exhausting It's cold where we live so he has to wear pajamas. Mornings he refuses and if I don't do it he's late for preschool or he could be having melt downs for hours. I'm pregnant and have a 2 year old and these struggles twice a day are exhausting. We've also tried bedtime chart and without fail he could care less bribery hasn't worked either with wither extra bedtime books snuggles one on one time or even matchbox cars or the option of picking what breakfast is. He is an extremely intelligent kid and he's a giant so he's already figured out his pregnant mom isn't capable of wrestling him holding him down kicking to get clothes on. I'm struggling with my stubborn almost 4 year old and I have a degree in Early Child Development and Family Science I should be better equipped then my current situation but I'm not and exhausted lol please help!