Well judging by your 200 time it seems that you need to work on speed. Your coach is wrong, you should not go over hurdles higher than competition height.
In terms of lowering hurdles, I have a couple of questions. Do you feel as if you are sprinting through the race and that you are sprinting through the hurdles? Or do you feel as if you are sprinting between each hurdle and then jumping over? If you feel as if you are sprinting through the hurdles, then you shouldnt have to lower the hurdles. However, if you feel as if you are jumping then you should lower the 2nd, 3rd, and 4th hurdles a knotch until you feel as if you are sprinting through those hurdles. After that, raise them back up to regulation and practice sprinting and maintaining a sprinting stride as you clear the hurdle rather than jumping over them.
I would emphasize speed at this point, with 20m flying sprints, acceleration work, and some 60m sprints as near to full speed as possible. Also, you might benefit from some resisted running (parachutes) once a week. In general, I would do speed work 2-3 times a week if there is no meet.
In the weight room, what lifts are you doing, what does your weekly routine look like, and what are your set and rep schemes?
Are you doing any plyometrics or jump work? If so, how many, what kind, and when do you do your jumps?
In general, I alternate sprint days with low-intensity tempo days to facilitate recovery. Could you post your current weekly routine and all its aspects (speed work, weights, hurdles technique, endurance, plyometrics) and the date of the meet you want to peack for so I can see if I could help you prepare for the meet.
Good luck, and feel free to ask any other questions.