Definitely go to a doctor. Whilst weed is neither a typical anticonvulsant, or a typical convulsant poison in the least in the latter case; THC DOES reduce neurotransmitter release, cannabinoid signalling via CB1 receptors (the subtype we like to tickle to get baked) acts differently, in terms of directionality from most neurotransmission. Endocannabinoids are, rather than released presynaptically, released in response to signalling activity from the postsynaptic terminal of a synapse, the part that receives the message being postsynaptic, usually whilst presynaptic terminals send them)
Endocannabinoids act as a sort of volume (in the sense of 'amplitude' rather than 'quantity') control. Released postsynaptically for retrograde transmission, acting on presynaptic terminals to reduce neurotransmitter reduction. This means amongst other neurotransmitters, GABA is one of them, as is glycine. The two primary inhibitory neurotransmitters in the brain. GABAa antagonists, GABAb antagonists can cause seizures. Not sure of glycine receptors in the brain, but the ones in the spinal cord are the target of the glycine receptor antagonists strychnine and its relative brucine. These are infamous as convulsant poisons, same with GABAa antagonists. Picrotoxin for example, coming from a plant, its been used to poison fish to harvest them for a long time by tribal groups. It works by acting as a GABAa antagonist, essentially working like the polar opposite of barbiturates (barbiturate/picrotoxin binding site is the same, the two are synonymous)
Reduction of GABA release if its powerful enough can have convulsant effects. I've often found that smoking weed, especially strongly Sativa types, causes intermittent, single muscular jerks. Not a seizure, just a random sudden involuntary strong twitch, say, in a leg if sitting down. CBD helps mitigate this, by its being a mild cannabinoid antagonist, possibly given the lack of similar foul side effects, acting differently from synthetic antagonists like rimonabant.
THC is a partial agonist at CB1. This means a ceiling on effects, beyond which effect does not intensify, only the duration of effect. Synthetic full agonist cannabinoids CAN cause seizures. A full agonist being capable of much higher reduction of neurotransmitter release, both inhibitory and excitatory, to the maximal effect.
GO to the doctor, first get assurances of the doctor-patient confidentiality, then reveal you smoked weed once guaranteed, that it does not go onto medical record (could make docs less likely to provide other meds that are abusable if you need say opiate, benzo etc. type meds.) and concealed from parents. AFAIK they are already legally obliged to make sure medical information is never given to others without consent. Make sure he or she knows you explicitly withold consent. And make sure the weed bit doesn't go on med records. Hell even tell them it was an accident and you thought someone was passing you a rollup, your first ever time smoking tobacco. Gives them the information they need to treat if need be, don't let them get away with not investigating further, especially if you have had seizures before or know you are prone to them.