If you increase your supply too much (by using fenugreek or similar) there's the danger that when your baby is at the breast he won't be able to drain it and get the fattier milk at the end.
When your supply has increased a bit you might want to try pumping one breast while LO feeds from the other, or pumping between feeds (I know you tried this already but after a few days of pumping you might have different results). This will help to make sure there LO gets both watery and fatty milk with each feed and in the bottle.
By the way, in the early days you need to pump more or less when LO gets a bottle to keep your supply up, once LO is 12 weeks you can relax a bit so long as you don't repeatedly give a bottle at the same time of day (this isn't as bad as it sounds, I mean if you want a bath or something you can pump before you go in and leave the milk for LO, it means you don't have to get put when LO needs feeding!)
For the pump- mine (Lansinoh) says you don't need to sterilise at all (only before first ever use). Breastmilk has antibacterial properties. Also the main reason you have to sterilise bottles is because milk gets trapped in the hole in the nipple, sterilising helps make sure bacteria don't grow there. My pump had no crevices where milk could get stuck.