I do not know where to begin. I know I am not the healthiest person. I think I look good, I am like 140 and 19. I am having so much trouble sleeping. I think there could be many factors to that. I just cannot sleep without taking a drink. Sometimes I lay in bed and think of all the things I need to do; I would not call it anxiety though. I am a smoker and I probably only eat one meal a day, typical fast food or going out to eat at a restaurant. I am very busy. In addition, it is not that, I mind so much not sleeping, just no else is awake and it is boring.
In addition, when I have sex in the missionary position my stomach kills, I have abdominal pain, and I do not know why or where it’s coming from. I know it is not normal and it never use to be that way.
In addition, now, my back and neck hurt, and I do not know what I did. I have good posture, so I do not know what I can do to help it.

I have very similar problems. I am currently 20 years old, and at 5'8" I weigh 125lbs, which is a very healthy weight, although I don't think I could run a mile . As you can see I am posting this at about 1:30am. I don't sleep, and when I do, I don't sleep well. It most likely a build up of stress, and my eating habits. For your benefit, and mine, I'll repeat some quick tips.

1. Try to avoid caffeine, but if you must drink it, limit it to one serving per day, either mid-morning or afternoon. 2. Do not eat anything at least 2-3 hours before your bedtime. 3. Cut down your sugar intake 5 hours before bedtime. 4. Obviously, eat a regular, portioned, well-balanced diet.

For sleep and your muscle aches, stretch. I don't usually have time to excercise, so I stretch while taking a shower. Roll your neck, touch your toes, stretch your arms, etc. all while washing your hair or body.

As far as the abdominal pain when having sex it could be a number of things. Your cervix could be curved, which you can ask your doctor about. Or, I've found that it's uncomfortable if I didn't empty my bladder previously. It's probably not the sexiest thing to excuse yourself to the bathroom during foreplay, but if it means a better experience, it's worth it.