In Virginia, the relevant statute would be Code of Virginia 18.2-248.1
I have linked you to the law. The marijuana offense is a Class 1 misdemeanor if the marijuana is less than a half ounce, or a Class 5 felony if it's more than half an ounce but less than 5 pounds.
The delivery or sale of one-half ounce of marijuana or less is punishable by up to one year in jail and a fine up to $2,500.
For greater than one-half ounce, the penalties increase to a possible 1 - 10 years in prison and a fine up to $2,500.
The concealed weapon would also be a misdemeanor.
More troubling would be the 8 ecstasy tablets, as this would be a felony charge punishable by up to 10 years in prison; fines of up to $2,500. And yes, once the lab confirms the weight and the nature of the controlled substance, the charge can be added to the case against you.
Nevertheless, even if you end up facing felony charges as this is your first offense and the charge is non-violent, a non-incarceratory offer will probably be placed on the table. It would involve probation and probably include random drug testing, possibly treatment, community service, fines. Some alternatives to felony incarceration can also result in no criminal record if the progrm is completed.
As you are a student who appears to be capable of good grades, if it is possible to avoid carrying a drug conviction around for the rest of your life, you would want someone who might be able to negotiate that. You should make sure you have a lawyer and discuss your case in depth with him so that you get a full picture of all of your rights and options.
Your lawyer should also explore trial possibilities with you. There may be search issues, for example, or other evidentiary problems with your case and, if so, you might wish not to avail yourself of a plea that would make you a convicted felon, even if it is a guarantee that you'll stay out of jail.
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This thread will not close and you can always use it to get clarification.This is informational only and is NOT legal advice.