Exercise-induced insomnia is normally caused by late afternoon or evening exercise. Are you on a low-carb diet or, alternatively, eating a significant amount of sugar? You could have a glycogen deficiency which can be helped by eating healthy carbs about 30 minutes after your workout. Also, increasing your Omega-3 intake could help reduce your cortisol levels that could be causing your sleeplessness. You could also try working out at a different time of day and see if this changes anything, but usually morning exercise is the best thing for insomnia.