Study suggestions

I think you've already studied all the basic stuff common to science under-graduation courses. I think you should think about your interests now and from that move to more deeper and specific subjects. If you just want to have fun with mathematics, give another chance to set topology (did you really study set topology?), it would be your first rigorous math subject and then move to real analysis. Try different books, the fact is hard for you it means you can learn a lot from that (I don't think is too hard from your background, ask questions here).


At the risk of swamping you with too much, you may want to look through past issues of the following.

Pi Mu Epsilon Journal

Quantum

Mathematical Spectrum.

Also, see the books in the New Mathematical Library series and the many translations of Russian "school level" books.