You don't get felony drug charges over tiny amounts of drugs. Usually it means the guy being charged was dealing.
Completely incorrect.
Most illegal drugs other than marijuana are a felony just to possess in any amount whatsoever. Steroids used to be minor but as of 2006 after the big baseball thing they became a felony too from legislation passed by Congress earlier. Most of the big body builders and pro wrestlers are now committing felonies on a regular basis.
Even just small amounts of marijuana was a felony in several states until recent years.
Possession of drug paraphernalia is often a felony itself even when the drug is marijuana and less than a felony. So the pipe to smoke the drug can be a felony even if the drug is not.
Even possession of prescription drugs you do not have a prescription for is a felony, as is simply giving one pill of something you do have a prescription for to a friend. Friend has some serious pain and you give them 1 pill of a prescription you have stored away from some injury or surgery years ago? Felony committed by both of you.
So pretty much anything except marijuana is a felony even in just tiny amounts for personal use. Even some forms of marijuana are a felony, like hash for example in any amount.
Possession of anything with intent to sell, even small amounts of marijuana is a felony, and cops will often charge people with that even for pot just for personal use.
Knowing some potheads over the years out in California who would buy several small bags of it at a time, if they were caught with those drugs they would be charged with a felony with intent to sell just because they are in multiple bags. Since many dealers have pre packaged certain amounts, anyone buying more than that amount at low level retail is going to have multiple bags of it even when for personal use. As a result they will be charged with possession for sales, a felony, even for small amounts that would otherwise be a misdemeanor or less if they are discovered by LEO.
So no, all illegal drugs can be a felony just to possess, and most except marijuana always are whether someone is dealing or not.
As for the OP. You have never been convicted of a crime according to you, so no you are not prohibited. If you do have a drug problem it would be wise to leave guns alone. Drugs and especially drug problems tend to lead to instability and often financial desperation. Which can be a bad combination with a firearm.
Even if you have cleaned up but have friends that use drugs, a gun is a valuable object, and many drug users eventually become thieves.