How to stay motivated in unrelated classes?

I apologize if this is a repeat post of anyone’s.

I’m in my 4th semester, currently majoring in Mathematics, and I’m actually on track to graduate a semester early. It sounds great on paper, but the only problem is at my Univeristy there aren’t enough 300/400 level courses in the Math program needed to graduate. This is a problem because I’m considerably uninterested in any class that isn’t math or physics. I’m taking 3 of those classes this semester, and it has been very hard for me to keep up. Two of them are in person, which haven’t been as hard to stay on track, but one is online, and will probably be the death of me. I dread doing 4 hefty assignments every week for a class that I could care less about. This has lead me to turn multiple assignments in late. I know somebody is/was in a similar situation, so if anyone could after me some advice on how to stay motivated and actually have a desire to get my work done I would greatly appreciate it. Thank you in advance!