Amitriptyline Hydrochloride and groggy

I have recently been prescribed this medication for severe migrain headaches. 25mg per night. I am concerned about taking this medication because it is an anti-depressent. I'm afraid of it affecting my personality. Has anybody noticed this? I tried to start it at night about a week ago, and didn't take another because I was so groggy and tired all day the next day. Does this side effect subside over time?

I am taking 25mg,its been 4 weeks now,i am tired/groggy all day,i feel cold,my mouth gets dry,i have constant foggy headaches,i was prescribed this drug to help with continual loose bowels,it definately helped with this but all the other side effects outway the good it does,on another article i read on a web page it says all my symptoms are due to amitrityline overdose----It makes you wonder do we really know what we are doing to our selves.