I did this as well. My advice is when you begin to apply for medical school, save up that stipend money and apply as broadly as possible, both DO and MD schools. If you get into an MD school, great. If not and you go DO, at least you won't be contracting into med services for four years. You won't have the opportunity to take a year off and apply the next cycle. When applications roll around make sure you have your apps in the first day it opens as secondaries will be rolling in soon after. You will probably be in LDAC when some of those secondaries come back so what I did was speak to the NCO or officer in charge of your platoon and politely explain how important a short turn around is for those documents. Mine allowed me to print them out, complete them, and mail them back while I was in LDAC. That way you don't have to explain a one month turn around. You might have some issues with scheduling classes concurrently with ROTC classes and labs, at least I did. The best tool you have is charm. Explain to your cadre early and often how important your classes/ MCAT prep/research/labs are. Some won't care, but some may cut you some slack. You want them on your side when you need time off. You might have a 3 day FTX the weekend before a big test.
If you don't get in and are still gunning for medical school after the Army (I'm just assuming you're Army), you have a few options. Obviously something medical would set you up for the most success. However, I was enlisted with a combat oriented job prior to coming to med school and I think it made my application stand out from the pack. That's just an n of one though. Pick something you'll be happy doing for four years because at that point, that's what you'll be committed to doing. Do the best you possibly can at your chosen career and reapply. Good luck, ROTC to med school is tough.
