I developed a sudden tolerance to alcohol, should I be worried? (serious)

I first started drinking alcohol around 14/15, only very lightly (like half a glass of wine or half a pint, so roughly 1 alcoholic unit), and even that was enough to make me flare up in red flushes and give me really bad headaches, or even throw up. I eventually gave up trying to train myself to drink and went sober for 2 years as I deemed I simply couldn't handle alcohol.

I then started drinking again at 18, still only very lightly, but experiencing the same effects, if not worse. There were a couple of occasions I drank barely 2 units, but was still enough to completely lose my vision temporarily - I would start feeling nauseous and see black/dark red spots until I couldn't see anything, and I would feel weak and lose balance/strength in my legs. I would force myself to stay stood up, making myself feel more sick until I threw up, which my vision would then return gradually over 5-10 minutes.

There was then one night I tried a glass of whiskey, and ended up throwing up twice. I tried again a couple of days later, except this time I felt virtually no effects, apart from a very mild red flush. So I had some more shots of moonshine and whiskey (I had ~7 alcoholic units that night), and I felt no alcoholic effects at all? I was (and still am) confused as literally every time I've drank, I've always had so many bad effects and have never been able to handle it well. Every time I've drank since, I've again felt very few effects from the alcohol - it's like I've developed a sudden immunity to it??

I'm genuinely concerned as to why I can't feel the alcohol getting to me anymore, other people have told me I'm just getting more used to it - which I don't believe is the case as it seems too sudden and too sharp. Is it just that I can't handle certain drinks but can handle others, or have I magically developed a genuine tolerance to alcohol? Should I be worried? My mum is allergic to alcohol and I'm asian if that makes any difference.