Lately, I have been feeling very weak and tired when I begin my warmup. My warmup usually consists of practicing some mild parkour techniques (speed vaults, lazy vaults, ect) and then followed by the APK Warmup. I notice when I start doing pull-ups in particular that I feel very light headed by the time I finish my 10th rep. When I let go I feel like I am on the verge of passing out.

Now sometimes before, I have eaten a pretty good meal and felt fine when I workout. I just cannot remember anything I ate from back then. If I eat TOO much right before I workout I feel a bit sick.

Also.... after workouts I tend to try to drink a lot of whole milk for some protein. I HATE the taste of milk but it's something I can do to gain some weight.

Any idea what I should due to solve this problem guys?
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Some important information
-Age: 17
-Weight: 127
-Height: 5' 8"
-BMI: I think I got a result in class that was 19
-Additional Info: I rarely eat any fast food. Once every other month sounds about right. I also only drink water, tea, tomato juice, or orange juice. No sodas or anything like that. I have been dabbling in body-weight conditioning for about 5 months or so now on and off. Nothing too serious just yet... I can't seem to get into the workout like I should be! I am also trying to gain weight, obviously.
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Oh ya... I have felt myself being very light headed during a workout one time. I was beginning some PPPU's and I started to throw up a little bit and then I passed out. I am not even sure how long I was lying there... just thought I should let you guys know.

Ahh sleep might be a huge factor now that I think about it. With school, work, and things I have been going through lately sleep is so hard to get! I just have been so stressed!

A lot of times that's impossible for me to just eat huge portions of meat. It really depends on what my mom likes to cook for the family. I do like to make my own things but of course my mother gets mad at me for eating something differnt, haha

I could give you a sample diet for sure!

Breakfast
(I very rarely eat breakfast, but occasionally I will grab an apple, banana, or pear.)
Lunch
-Hamburger (lettuce, tomatoe, pickles)
-School french fries (I forgot about these )
-School brownie or cookie
-Banana
-Brocolli
-Cauliflower
-Red Beans
-Green Peans
-Peaches
-Choco. milk
Dinner
-Lean chicken/beef of some kind
-Baked Beans
Snacking
-Berries
-Salad
-Fruit
(Also, all through the day I will only drink water. If I get home I will drink some of Milo's tea or tomato juice, though.)

Like KC said, definitely try and get more sleep, at least 7-8 hours a night and more if possible. Also, if you don't like large quantities of meat, try looking for a good protein powder to mix into a blender with milk and ice. I have one named Smart Gainer Vanilla Cinnamon and it makes my shake taste just like a cinnamon roll  It also comes in a large bucket so you want be buying it every week.

My recipe if you get Smart Gainer

Fill the blender half way up with milk and ice, then put in 2-3 scoops of powder, blend, and enjoy