Need help with a 27F (doctor prepping for masters) with anxious attachment dating a 28/M avoidant attachment busy (resident surgeon) man, please?

I have been in a relationship with him for nearly 1.5 years. I was always so in love with him and obsessed with everything he did to an extent where I found myself constantly looking at his location details, checking his phone, stalking his profile time and again. He started his residency in surgery 4 months back and he has been busy ever since. We don't get time to talk like we used to. I was emotionally dependent on him. He always tells me to look for my hobbies, study for my exam and not invest my time on him or thinking about him. I have been trying to not think about him but GOD, HE IS ALWAYS THERE INSIDE MY HEAD. I know I should be studying but I am insecure, obsessed, looking for ways to make him feel better, scared that he will cheat on me. There was this incident few weeks back where I found his chat with a nurse where he was flirting with her (healthy flirting eg. where've you gone, you're needed in the ER right now! I'll come to work with you if you don't, etc.). He isn't the type of guy to do such a thing because I know him. We were arguing every 2-3 days because I didn't like the fact that he used to go out every other night with his friends and drink after his duty. I used to bombard him with texts and calls and he hates anyone who would annoy him or make him lose his sanity. And now we're doing okay because I don't text him much and he calls me whenever he gets time. But me being an overthinker and insecure woman, I expect him to text me whenever and wherever. Also, it's always me who asks him to meet me and I get bothered by it because of financial restrains. WHAT SHOULD BE DONE