If you can do anything to fix your sleep now, immediately, it should be done. Poor sleep is arguably the worst possible thing you can inflict on your body. It has direct links to virtually every major disease and ill health outcome, including cancer, alzheimer's disease, every major mental health disorder, heart disease, increased risk of physical injuries, decreased metabolism... The list continues.
You should absolutely get your diet under control and build a consistent exercise routine in the long run. But both of those things will be very hard to do without the proper dose of high quality sleep every night. Without proper sleep you'll be fighting your own body every step of the way. Every positive health outcome gets harder to achieve without sleep, not easier.