Sure - Please suggest. I have been buying books (the likes of Apostol, Spivak, Artin) and doing self study. The typical pattern is start solving the problems and I get stuck with tough ones. And I hardly go past the third chapter of all the books that I had bought because of this.

Being unable to solve some tough problems is entirely normal - there is only a handful of people gifted enough to go though a mathematics curriculum, getting 100% on all their assignments, working in isolation. I certainly didn't! Having been a TA in upper-level math courses, many/most of the students averaged 80% on homeworks which were certainly NOT made up of entirely tough problems - and they probably worked together quite a bit, and had teachers to ask for help if they want. So don't get frustrated if you get stuck regularly, just move on, then come back later in a couple of weeks when you're reviewing and try again. If you're still stuck, go to an online forum to ask for a hint, or you don't have to feel guilty about skipping some of the hardest problems entirely.

Two book suggestions:

Strichartz - The way of analysis. MUCH more user friendly than the standard analysis texts. The book is filled with long paragraphs if english sentences explaining what your are doing, and why you are doing it (if you can imagine a mathematics book committing that sin!).

Pressley - Elementary Differential Geometry. The appeal of this book is that it teaches only the more concrete classical formulation of the theory, so you don't have to confront tensors and n-dimensional abstractions at first, and also that it provides outlined solutions to every problem in the text!

Armstrong - Groups and Symmetry is accessible. Munkres - Topology also doable. Vector Calculus by Marsden/Tromba was my intro calculus book however im not sure if calculus is ever going to be very interesting. not a bad book though.

What areas of mathematics are you interested in learning about? I would also pick up Principles of Mathematical Analysis by Rudin.