I would work on not getting caught up on how 'stupid' you think you are. That will get you nowhere...it just contributes to a lack of motivation.
It's not about doing something more, it's about trying something different. Don't get caught up in this idea that you tried as hard as you could and it didn't work so nothing will, you're just stupid...where the hell is that going to get you?
If you try Psych and it works for you, go for it. Major in it. However, I would continue taking your prereqs (maybe at a slower rate) so that you can try a crap-ton of different study strategies until you learn what works for you. Try and write exam questions for yourself - it gives you a good idea of what your prof will try to trick you on. Half of solving any question is thinking to yourself "what is it the prof is trying to see if I know with this?" Try Anki. Try outlines, try multicolored notes, try things until they work. Look at why you find Psych easier and see if you can bring some of that approach to your other courses.
If you just sit there thinking 'I am stupid, I should just wait and take these on easy-mode because I will never succeed at this level' you won't push yourself, you won't try new things, and you won't figure it out. This is worth figuring out - it's a skill that will help you tremendously if you continue into med school.
