I have man boobs from the age of 13. and they growed day by day. now i am of 18 years and have very large boobs . is boobs will go after a few months

Depends on the situa: Pubertal gynecomastia will occur in 1/3 to 1/2 of males ; generally last about a year before fading.Up to 3 years is noted occasionally before disappearing. Overweight kids can appear to have it from just fat accumulation.If present after 3 years, surgical removal of the glandular tissue ; liposuction of any associated fatty tissue will do the job.

If you have had: Pendulous breasts for the last 5 years ; nothing else has changed then there isn't a reason to believe this will change over the next couple of weeks. If you are obese and lose weight - your breast size may also diminish. Encourage you to see your doctor for assessment. Sometimes endocrinologic issues can play a part. Some men have plastic surgery to reduce breast size. Take care.

Hard exercise helps: Exercise, exercise, exercise alongwith controlled diet. If the manboobs developed but you are normal weight for your height then ask your doctor to rule out medical reasons for your problem. Treating the cause can help reduce the problem. If not settling then see your plastic surgeon for corrective surgery.