Exclusively Pumping HELP PLEASE

Ladies who exclusively pumped please please please help me. I’m on the verge of a breakdown. My baby girl was born at 36 weeks and is extra lazy due to being so tee tiny. She has latch problems in that she will latch but because she gets worn out so easily she will lose my nipple. So, we are moving to mostly exclusively pumping. She is only 6 days old. Did anyone pump solely from the start? If so, how much did you pump per session? I’m really starting to worry that my milk is coming in at a horrible amount. I only pump about one ounce combined every 3 hrs. Please tell me this is normal and my milk will gradually increase to what she needs!