Sour Diesel/Purp Makes Me Abnormally Sleepy

Just recently, I picked up an eighth of Sour Diesel/Purp (not sure which strain). It's supposed to be dank medical bud from Cali, so I was really excited to smoke it. The problem with it is, even if I wake up late in the day (say around noon) and have enough coffee in the morning, if I toke around 10, then I usually become way too sleepy to function in about an hour and a half. This is very frustrating, because even though weed is supposed to help you to fall asleep, I feel like this strain makes me excessively sleepy, and I am NOT exaggerating, trust me. Normally, even if I smoke enough of an Indica strain to get fairly baked, I am usually able to stay awake and do stuff for 2-3 hours after I take a hit late in the evening (after 10 PM). For example, there was one week when I was only smoking Pineapple Kush, which is an Indica strain, and I was able to stay up until at least 1 in the morning. Now, even if I only take 2 bowl hits, which only gets me moderately high (not baked), I will become excessively sleepy within about an hour. Also, if I only smoke hash instead of weed, I can get ripped, and enjoy it for at least 3 hours before falling asleep. What could be the reason behind this phenomenon? I am trying to figure out what could be causing this, but haven't been able to come up with a solution. :mad: