First, why do you think you need to avoid carbs all together? There are a few things that you need to get in order to be successful at getting back in shape.
Here is the basics:
1. Switch to free weights...that machine thing sounds like an excuse
2. Choose 3 exercises: one push, one pull, one squat variation
Day #1
Heavy Push 5x5 @ 2 min rest
Moderate Pull 2x12 @ 1 min rest
Light squat 1 x 20 (you'll feel a tad queazy if you do it right)
Day #2
Heavy Pull 5x5
Moderate squat 2x12
Light Push 1x20
Day #3
Heavy Squat 5x5
Moderate Push 2x12
Light Pull 1x20
Use the same exercises for 4 weeks straight and then pick a new push, pull, and squat variation.
Eat 6-7 meals a day.
Eat large serving of non-processed, vegetable based carbs 2 times per day (no fruit)...first thing in the morning with protein and immediately after workout with protein. The other meals should be protein and healthy fats (salad veggies are acceptable).
Drink nothing but water.
There you go. As to your arms, I can't really tell from the photos, but it looks a lot like you may have stretch marks. It is a common thing with people your age with all the hormones fluctuating and raging through your body. If it is not stretch marks, maybe you should have it checked out by a doc. I can't really give you an accurate piece of advice without seeing you face to face.