Hello,
Delay in menses can be due to pregnancy, stress, hormonal imbalance, imbalanced diet, excessive exercise, depression, thyroid problems, poly cystic ovarian disease etc .If your pregnancy test is negative you can get a blood for Beta HCG done to confirm. If it is negative it can be due to the above mentioned causes. In your case, excessive weight can be one of the reason.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Honestly it could be caused by your weight. Excess weight can influence the hormones in your body making you skip periods or stop having them all together. Stress could also be a contributor too. But the best way to ensure a future healthy pregnancy is to try to loose weight regardless of weather or not your weight is currently effecting your periods. I know it's easier said than done as I'm trying to loose my extra 50lbs. But being obese can increase your chances for a premature baby, gestational diabetes, preclampsea, and other complications so I'm personally not considering getting pregnant until I loose my weight and I think you may want to look into doing likewise. You definitely need to be healthy for yourself, but you should also consider it for any hypothetical baby in your future.