Why am I stoned/high?

Several months ago I decided to quit smoking weed and have not touched the stuff since.

Last night I had a late night with my girlfriend and did not get to sleep until very late. It is now 4pm and I have just woken up, and I am sure that I am stoned.

My face is all droopy, my eyes are red and I feel like I have smoked about 5 joints. My head is all dizzy and slow and light feeling, and I feel a strong urge to laugh.

I smoked weed for about 11 years so I know what it is to be stoned and this is it. I am not sleepy or anything like that, I am most certainly stoned.

Any ideas why?

At the moment I’m assuming that I still have THC in my system or that the feeling stoned is an effect of the THC finally leaving my system.

Has anyone ever felt this before or read anything about this happening?