I took 4 years of bio and chem in a rigorous college prep high school, and did well, including the AP classes.

You'll be fine. Lots of students enter college coming from shitty high schools and colleges advise freshmen to take a light first semester so that they can adjust. Students who have a strong high school education tend to not struggle so much, especially if they had to work hard for their grades. Grade inflation in high school often leads students to struggle in college because if you get A's without putting much effort in, shit hits the fan when you have to actually study. If you built a good work ethic while getting a rigorous education in high school, the transition to college will be pretty smooth and you should have no problem handling bio and chem in the same semester.