My school only offers 13 Ap classes what should i do

Here is the decision tree I recommend following in your situation:

1. Ask your guidance counselor if your school is partnered with an online AP course provider. If they are, then you could take AP Comp Sci and other classes during the school day. The way this typically works is that you will go to your school's computer lab during your online class periods. You will receive high school credit for these classes and they will appear on your transcript. Colleges will usually give you credit for the classes as well if you score between 4-5.

2. If you cannot take online AP classes, try to take equivalent classes through dual enrollment.

3. If you cannot dual enroll, then self study for the AP classes you wish to take. You will not receive credit from your high school for doing this, but many colleges will give you credit for scoring a 4 or 5 on AP exams.

As for your other question, I think that you should take APUSH. It sounds like you are taking a lot of STEM classes already, so APUSH would round out your transcript. It is also not the most difficult AP class, and it teaches you valuable analysis skills which are applicable to any career field. Hope this helps!