Struggling with Sleep Schedule: Need Advice

How can I develop a healthy sleep schedule? I'm at a point in life where it doesn't really matter when I'm awake or asleep (I'm not a student, I don't work outside the house, and I don't have responsibilities that need to be done at a certain time of day). Still, I feel more mentally stable when I'm able to sleep at night and wake up in the morning. I have trouble initiating sleep and haven't been falling asleep until morning (after 7 AM). Even if I take a sleep aid, I struggle horribly with actually sleeping at night because my schedule is all messed up and nothing seems to set it straight. I've been waking up in the afternoon (after 3 PM). Again, I don't really have to worry about needing to do things at certain times, but I do get really bad anxiety just from living such a disorganized and inconsistent lifestyle. Also, I'm going on a trip later this month where most activities will be during the daytime, so I do need to be awake for that. I'm really feeling hopeless and distressed about this right now, so any advice would be appreciated. Thank you so much.