ex (m, 23) broke up with me (f, 20) to explore sexuality and is now dating a man after 1 month and im so depressed

what’s up with this? he always emphasized the importance of connection and what not but finding someone new to just date right away? bringing him over to his apartment? showing him around the town and bed I was in just last month? it hurts so much because I tried so hard and recenrly he’s been struggling a lot with his graduate school rejections (15 so far) and has been calling me every night to cry about it. I thought we were still each others people and now I guess we’re not and I’m not special anymore like that