It is actually quite common to not be able to wind down. A lot of people struggle with it. It may not be for exactly the same reason with the research but it is still pretty common.

Have you tried any relaxation techniques? For some people they can work extremely well. Try focusing on relaxing your body slowly. It gives you something else to focus on and can help you relax.

Also, from my previous work I found that a lot of people with sleep difficulties could overcome it in time with a strict bedtime routine. As a psych major you may have learnt that your body can associate actions and feelings with different routines and objects. Even if you can't sleep it might be worth starting a night time ritual. Eg. getting changed into pjs, brushing teeth, reading for 1/2 hour and then trying to sleep. If you find after 1/2 hour you can't sleep get up, have a drink and start the ritual again. It may sound weird but in time you can train your body in that ritual and that it means time for bed. With that, if possible try to leave your bed as only for sleep - don't sit and do your research in bed at any time of the day.

Not sure if this helps but I hope it can. I know a lot of people who have been able to overcome their issues falling asleep in time using similar techniques