Scared to start pumping

Baby is 4 weeks old today and I was told by lactation consultant at the hospital to start pumping around now... Since baby was born I have been using a Hakka and catching my milk. I have a pretty good supply so far just from catching.

My breast are already over engorged at times and make my little man throw up sometimes.

I'm scared to start pumping and having my milk come in even more and he continues to Throw up because my breast are so full...

What should I do?