Not a good weight

My male bp, whom i've had for about 2 months now, does not weigh what he should (partly because he didn't eat until about a month ago) and I don't know how to get his weight back up. He was born in November, is 22 inches long, and weighs between 125 and 150 grams. He receives a weaned mouse once every 4-6 days. Any tips?

He could probably eat a full grown mouse at this point. Go by how big around he is at his thickest point, the prey can be as big around as that.

Just my two cents worth.....