Just know that I am not a professional in the clinical sense. As far as I know, none of us are. I am a first and foremost a linguist that branched out to other fields to study psychotic disorders. I know the essentials of quite a considerable part of the scientific literature on psychotic disorders, including BP. Some clinicians have lots of experience with the likes of us: those with psychotic disorders, some mainly BP. It's always good to have someone with antennae like that.

That said, we also have a lot of (combined) experience here. Many of our problematic behaviour is essentially the same, but more so than we might care to admit, many particulars one might display have been previously seen in other individuals too.

From what I gather from your post about impulsivity coupled with lots of energy and risky behaviour, I'd say BP is very likely. Probably you have had some mania or hypomania. Functional impairment (severity) can tell you which.

Prodromes, so not actual, severe symptoms yet, are common in childhood. Developing BPD (or the first signs of any consistent personality) generally happens/starts just a few years before puberty into adolescence, most probably. The personality develops as a mechanism to deal with any problems. Memory problems are a strong indicator of psychotic prodromes. BPD is not an uncommon way to deal with it (many/some here have it). I had/have (much of) it. Still, personalities vary greatly of course. A personality disorder category/label might just points to somewhat dysfunctional characteristics of your personality.

A good psychiatrist would be very much interested in accounts (by you, your boyfriend and your mum) of your childhood and later years. If not for firmly establishing that you have BP (as far as childhood is concerned, it can't tell you everything), at least to establish what it is not (for example, an autism spectrum disorder, which is more severe in childhood than in later life, generally, and which is also related to outbursts of anger).

If I forgot to address anything else you wrote, please tell me. Good luck in preparing for your appointment. Read posts here and in other forums to see whether they resonate with you (of course you've done much/some of that already).