I took the usmle a week before the comlex with no problems. Most of my classmates took it a few days before or a few days after. This is what I would highly recommend. Some of my classmates decided to wait a few months after to take it and most of them, not all, wished that they would have scheduled it at about the same time as the comlex. They found it difficult to find enough time to study the way they wanted to because of the workload during their clinical rotations. They also realized that the time you know the basic science material the best is right after you complete your second year, not 6 months after clinicals. Whether you take it before or after the comlex IMO makes no difference. Be aware that after you take the first exam that you will be completely exausted and it will be difficult to continue to study at the same pace. Not to mention the feeling of "I can't believe I have to take another licensing exam next week". It really wears you down.
Hang in there.