I'll give some more details.
My character starts at lvl 17. Save file says it's 18 but it's 17 - i only have 10 feats. Now i can do 2 things:
1) Open lvl up screen, proceed with lvling up once. I end up at lvl 19 with 186 HP, 11 feats and 80 invested SPs more than i had at lvl 17. Seems correct, except i jumped 2 lvl at once.
2) Qpen lvl up screen, cancel lvling up, open again, proceed with lvling up once. I'm at lvl 19, 186 HP, 10 feats and 40 SPs more than i had at the beginning.
Yes i do cheat. Speedhack and no weight hack. I started using no weight just recently so if it's because of cheating it has to be this.
I managed to get out of this situation. I'm posting it also to warn other players because it can be very unpleasant.