I was wondering if there is a antihistamine similar to Doxylamine Succinate (Unisom)?

I've been to 3 diff allergy docs an have tried Zyrtec, Zyrtec D, Claritan, Hydroxy Hcl (worked a lil), Allegra, 4-5 nasal sprays an many other things. I have yet to get a doctor suscribed medication that has worked sadly. They started to just say that my nose is sensitive after testing me. Idk about that bc i only sneeze in certain areas. I think its dust an mildew an some other that im allergic to but still no med has worked.

 Then one night i was really tired of sneezing an just plain tired so i took nyquil to sleep. I woke up in almost heaven. I know that sounds silly but this allergy or w/e it is, is year around. Anyway i took the nyquil an woke up with my nose clear, i sneezed maybe 2-3 times the entire day an slept great. So i tried it a few nights more an same affect. 

I soon learned that Doxylamine Succinate (Unisom) works great on me. I even took the antihistame seperate from nyquil. My only problem is that it does induce sleep an makes me really very tired. Im learning to wake up an take it so i wake up allergy free an not so tired but i dont wanna fully rely on it.

So my question again is: I was wondering if there is a antihistamine similar to Doxylamine Succinate (Unisom)?