Since this is your first year and you're just getting used to the ins and outs of tricky female ball pythons, the best advice I can give is to keep on pairing up until the females are no longer receptive ... as long as that takes ... you'll get eggs.

The difference between "building" and ovulation is difficult to explain in words, but once you see them both you'll know for sure ... When females are "building" they look like they are gaining weight all over but when you hang then vertically out of their tubs you'll see a baseball sized lump mid way to 5/8th's of the way down their bodies ... if you run your fingers under their bellies and apply some pressure, you might even be able to feel the follicles (the process of palpating) ... Ovulation on the other hand, make the female look like someone stuff an oversized nerf football inside the girls ... it's a HUGE oblong lump that stretches a good lenght of the girl body ... they almost look like they are teetering on the lump ... it's hard to miss and within 24 hours they go back to normal.

Hope this helps ... let me know if you have more questions ... as always, anything I can do to help you've got it!

Sounds like you're well on your way to a great first year ... congrats!

-adam