Is there a way to get more upgrade points ?

Ofcourse. Complete slaver guild quests or sell tamed slaves. 

I have been getting my slaves pregnant and then selling the babies once they grow, I usually first fix them in the lab to be more attractive, then increase their rank and dispine them. i usually get 5 points per slave when i sell them as nobles. 

Non-Captured, high Obedience slaves will earn you upgrade points equal to their grade. I usually do mass slave-taking runs.

• Take 20 ropes, head Deeper and grab every pretty-looking Commoner, or anyone of better grade.
• Head back to town once I run out of ropes, buy teleport stones to send the Rich and Nobles straight to jail
• Quicksell the rest, then settle in for a round of slave-breaking. Mostly I throw Fear and Sedation around like it's going out of style.