Hiya 
First off it isn't for no reason that he is waking. There's a reason however tenuous - maybe he is teething, maybe he is hungry, maybe he just sense you are not there and wants to be near to you.
Finding the reason and responding to it is a better answer than giving him drugs he doesn't need.
I haven't heard of anyone giving a baby phenergan. If there is a risk associated with it I am not surprised - it is an antihistamine and therefore makes you sleep more deeply.
Babies who sleep more deeply are less able to wake themselves should they forget to breathe (not as odd as it sounds - mine has sleep apnoea, it is very common and means that occasionally he will just stop breathing very briefly and so, if he were to be sedated, he would probably not start again.
It could even be that he is waking because of some kind of problem with his breathing - babies often wake due to apnoea. You wouldn't know it had happened, just that he was now awake.
Please don't medicate. CC at less than a year old is also not recommended. Babies do wake frequently, often, and it is not a problem, it is just what they do.
Sorry you are feeling so rubbish. But please don't give him any sort of medication to make him sleep.