Sleepy

So everything I know about adipex is it's supposed to make it harder to go to sleep than to wake up. Before I started taking adipex I was taking about 10 mg of melatonin to get to sleep at night (I've always struggled with being able to get to sleep). I was a bit worried about being tired enough to sleep so I decided to take only half a pill. I've noticed though that I get really tired in the afternoon. I'm taking naps like never before. My husband wants me to take the other half of the pill with my 10 am meal so I'm not so tired in the afternoon/evening, but 1. I'm cheap and want to cut my pill costs from $50 a month to $25 a month and 2. if this dose starts to lose it's effect I want to be able to take a whole pill instead of increasing to one and a half or two pills and 3. like other drugs, you can develop an attachment to adipex and I don't want that to happen.
I'm going to check my blood pressure today at the gym to make sure it's not gotten too high as that can be a common sign of daytime sleepiness. I've never had high blood pressure so hopefully this is just how I react to the medicine, kind of like those mom's who say benadryl makes their kids hyperactive instead of sleepy, I'm hoping that is the case with me.
Another possibility is that I'm doing much more than normal and half a pill may not be enough to cause insomnia. Mainly I'm great during the day as long as I'm up and doing something. Yesterday we went to the park and I stood almost the whole two hours without having pain (which is amazing as I normally can stand no longer than about 5 minutes without experiencing pain and needing to sit down). I was out in the sun and fine. But as soon as we got home and got the kids down for a nap, I went to my room to watch some tv and I fell asleep. Part of the problem could be that I haven't gotten to sleep before midnight for about the past week (and sometimes not until 2 am), though this is not from a lack of being tired so much as the kids were arguing for a long time while trying to go to sleep (they share rooms) and I had school work etc.
Anyway we are leaving for the gym in about an hour so I will check my blood pressure before I work out and see what's going on.