Definitely not strange for your milk to take a while to come in. Try the nipple shield (I had a lazy nurser). Make every attempt to nurse him for a while, and then after he is done, pump for 10 minutes. If he still seems hungry when he comes off, offer him some prepumped milk or formula. You will never be able to pump out more than he can suck out on his own - they are much more efficient by far. I think at that age, mine only took about 2 oz - 2.5 oz a day. If you are getting wet diapers, he is getting milk.
I think my milk supply yo-yo'ed a lot - sometimes I leaked everywhere and some days I felt like I had nothing. Even now I feel like I am really full for a week, and then I wonder what happened to my milk. Plenty of water (and if you can believe this - rest!) is what helps make milk - and his sucking is best - if not the pump. Some of the best advice I heard once was if your milk supply is down, grab your favorite book, a huge jug of water, and your baby, and settle into bed for a 24 hour rest - hydrating - suckling/stimulation marathon. (add bonbons to that I know, like any of us have time for that!)
Just feed him when he is hungry, and if it seems like no matter how much you feed him, he is still hungry, then offer to top him off with the bottle. Your lowest milk production time is in the evening, so this is probably when you will need to top him off. Just remember to pump a little if you offer him a bottle, to let your breasts know they need a little more!
Hang in there!