Hey Rui,
Here you go:
http://www.mutopiaproject.org/ftp/RachmaninoffS/O3/rach-prelude-op3-no2/rach-prelude-op3-no2-a4.pdf
Sorry, better address this before I forget about it yet again.
So I considered the sheet music and a video of the piece being performed. The dynamics and the tempo may be the two simple reasons behind your struggle.
Section 2 is obviously faster than section 1 (I mean come on, section 1 was in Lento). Instead of hitting multiple chords, you're now playing through melody and accompaniment. You're basically from hitting a ton of notes at once to working through a whole series of them.
Your exam is in September, so you still have plenty of time. Practicing slow is still very much important at this point even though it sucks. Instead of focusing on how accurately you can hit every note at a solid speed if not performance speed, take it easy and ensure you have all the details brushed up. Then, don't be in a rush to accelerate to performance speed either; build up.
Section 3 is more like section 1, but there's two noteworthy differences. It's a lot louder, and whilst it's slow it's become jumpy. Your arms are definitely going to sweat a bit because you're going from one end of the piano to the other continuously, and when performing this you really need to produce the
fff and
sffff somehow. Being blunt, this is something I would say cannot be helped. I had it a bit more bizarre; last year my back ached when I was practicing a jumpy section or used pedals. Sometimes I just had to lie down after playing it once because I couldn't help it. But after a while it stopped because I got used to it, so adaptation does happen.
Personally, when I play piano, I also usually just wear a T-shirt and shorts. I sweat quite easily when I'm on the piano so I compensate for it somehow. Not saying do that in your exam, I just mean for practice.
If you really want to minimise the annoyance on your body, try cutting back on tempo and dynamics instead of aim for the performance-level playing. Remember, there's still 3 more months to go. You definitely want to start aiming to reach the full performance level, but it's still not time to make sure you're always playing at that level either.