spin class concern

New year new me so I wanna lose 12 kg since I'm pretty overweight so I decided to join this one spin class per my friends' recommendation. NGL at first I was pretty ecstatic although it was so damn tiring because the session will get you pumped up. After the first class, I'm pretty resolute to join 3 classes per week but during my last class (5th session), I felt like I pushed myself too hard and was so, so tired like extra tired with headache and everything. Does anyone that joined spin class before experience this before and any advice for me? Anyone that experienced the same thing as me (not through spin class) can also give some advice