Is it normal to feel tired after smoking cigarettes or pot?

Weed always makes me sleepy

If you don't get much sleep you will be tired anyways. Smoking makes you relaxed. You're just ready for sleep when you smoke at night.

Sometimes I get sleepy when smoking weed but never with cigarettes

Weed does tend to make you sleepy... when I was new to smoking sometimes I'd just knock out early when I got home from a heavy smoke sesh at my friend's place.

Cigarettes generally help to keep me awake though, unless it's an American Spirit or something like that and I get a nicotene buzz.

Nicotine is a stimulant the same way caffeine is (albeit to a lesser extent). You really should feel more alert than tired, but it is relaxing as well as it reduces stress. I do the same thing. I don't smoke more than one cigarette a day and it's always right before bed. Its like a ritual almost, but I won't really feel ready to sleep without it.

Stop smoking cigarettes and pot.

It causes your lungs to take in less oxygen. Combined with the fact that you're already low on energy for the day, it is the final blow in making you sleepy before you otherwise would be.

You shouldn't do either.