I have marks under my arms? look like cuts but they are wide and i dont know what they are

Exam needed: These marks have to be inspected by your physician or dermatologist for diagnosis. They could be stretch marks.

Stretch marks : These are likely to be stretch marks, which appear in areas of your body that undergo rapid growth, particularly common on the tummy and thighs but also found in other areas such as under arms. It would be worth seeing your GP for a proper diagnosis. Have a look at this link http://www.healthline.com/health/stretch-marks#Overview1

Marks: sound like stretch mark and they are harm less. but if there is pain or signs of infection then FU with GP for a review.

Stretch marks?: Have you lost or gained weight recently? Have you been on steroids? Have you put on muscle mass recently? These are some of the possible causes of the condition you may be describing.