Corey. You can't take marijuana ever again if you enter the USCG. Also, if you make a career you will be polygraphed as part of the vetting process for certain clearances, and you can't lie. I am not going to come out for or against mary jane, but the facts of the matter are as stated. They are generally forgiving of teenaged experimentation.
These "Natural" colon cleaners are not usually regulated by the FDA and may have substances in them that are not on the label. I suggest you eat healthy, exercise the old fashion way (not the quick dehydrate yourself way) and stay away from all drugs, herbs, or "natural" supplements / cleaners for >30 days so your body is fit to go into the USCG.