Feeling crappy...

I was M.E. for BS and MS. Don't get discouraged. 72% isn't bad, it means you know most of the material. You must be bright to be in those classes your 1st quarter. Later engineering tests may have average scores of 60%. That isn't failing, just a challenging test that separates the workers from the whiners. We loved Calc III in Jr College because the prof was a retired civil engineer and could readily explain integrating pressure on a dam. The same concept to calculate Mean Effective Pressure in an engine cylinder. Perhaps you have a math dweeb like my Diff Eq prof who couldn't even derive the spring-mass oscillation.

The math doesn't get harder, except electives. Diff Eq is mostly learning little tricks that nobody uses today. Variational calculus is challenging but interesting. The problem with engineering is you don't start most classes until junior year, but maybe sooner since you are way ahead. Statics was amazingly easy. I got 100% on every test, with minimal effort, just Physics I again. I couldn't understand why others were flunking. Thermo was the most challenging, but also so interesting I switched to ME. ME mostly expands on classical Physics. You can focus on thermal/fluids (interesting) or structures (boring). ChE is just ME in a process plant and AE is just ME for aircraft. EE is the only one a bit different. I have worked as ChE, AE, and EE.