Chnging a levels

I changed from psychology to chemistry because I thought i might’ve wanted to do something sciency in the future. But now, I’m thinking of doing engineering but I searched up lots of universities requirements and it seems like i definitely need physics. Before choosing any of my a levels, physics was in my mind a lot but I didn’t choose it because I already chose maths.
I’ve already changed my subject once, can I change it again? I’m already in a levels for 3 weeks now. Is it possible to catch up the work? Should I change subjects or should I just continue with chem?

Continue with chem unless you have the actual burning desire to become an engineer. Stop changing on last minutes, more than once is unhealthy. You're gonna be behind a lot of content and ahead for a lot of stress at this point.

I do reallyyy want to be an engineer. It was my plan all along well besides architect. I wasn’t educated enough and I didn’t research enough before choosing my a levels. The thing is I thought i only needed maths.