Intermittent Fasting

I’ve recently taken up IF as it fits my schedule better. I’m a premed and this semester they crammed all my classes in the morning-early afternoon. I break my fast after my last class ends at 3 and go til 11.
Previously, I was eating 4300 kcal/day. I started IF with 4500 kcal/lifting day and 3300 kcal/off day. This added up to a 4300 kcal surplus a week (6 on 1 off)

At first there was a large drop in weight. I’ve been slowly increasing cals by 100 each and am now at 4700/lifting day and 3500/off day for a weekly surplus of 4,500. I’m still not gaining. Is this normal on IF and should I increase cals again?