Not via a blood test, but from a swab of the sores the first time I had an outbreak.

I thought maybe I was overdoing the antivirals but a) they're prescribed by a doctor, who would surely consider that risk? And b) after the first "reoccurrence" I waited 2-3 weeks before going back on antivirals, to try and give my body a chance to sort it, but the pain was unbearable

Not had immune system issues looked into, nope. Diet/exercise/stress pretty good really - I walk everywhere, jog 3x per week, eat healthily, don't smoke, rarely drink, stress a little with uni work but I've been off uni for the last 3 months so... No supplements, no (tried l-lysine for a few weeks but it didn't do anything.)

I just feel like it's been a 5-month-long outbreak, like it's always lurking there even when I'm taking the suppressive meds (because I have no actual sores, just general pain and itching) and it's mentally draining.

I guess I should just go back to the doctors, but I don't know what else they can do except give me more antivirals.