I came to medicine from a similar background. There was definitely a learning curve when I switched to the hard sciences - it wasn’t impossible, but the difficulty threw me a little bit at first.
My hardest psych class was comparable to a moderately difficult premed class in terms of workload and time required to master the material. Be prepared to put in hours, and they will be long ones. That was the most difficult mental shift for me, I think. With the social sciences, I could pay decently close attention in class, take pretty good notes, read the chapter the night before the exam and pull 90%+ scores no problem. BCPM courses are a totally different animal - I put in HOURS of work every day to earn As. But, like anything else, you adjust to it after awhile.
You need to plan on studying and doing practice problems every day. Brush up on your math skills if you’re rusty. Go into your professors’ office hours as much as possible. Utilize learning resources on campus where necessary (tutoring, study groups, etc.) Also, consider taking a lighter science/math courseload your first premed semester, just to give yourself time to adjust.
The switch is hard, but doable if you’re motivated.