Sorry, but I don’t think that’s anything like a definite diagnosis, no. It has to be in person, with a neuro. And finding lesions on MRI is not, by itself, enough to diagnose anyway. Have you definitely had at least two distinct “attacks”, or experienced continuous deterioration for at least a year? Have you had blood tests to rule out absolutely everything else? (Other conditions can cause lesions). Have you had a lumbar puncture and/or visual evoked potential tests?
Unless the majority of these are true - particularly having at least two attacks, or one year’s continuous deterioration - you might get a diagnosis of “possible MS” or “probable MS”, but NOT clinically confirmed MS. It’s possible to have a one-off “MS-like” attack that causes lesions, but never goes on to be repeated. So unless it’s conclusively demonstrated it’s an ongoing problem (further attacks and/or deterioration) it won’t satisfy the “multiple” bit of MS.
Your GP is NOT qualified to diagnose MS - even if they have enough knowledge to say that’s what it looks like. It could still be other things that are similar, but not the same. So no, I’m afraid you can’t consider yourself diagnosed - and it may still be a long road before you are (IF you are).
You do not need to tell anyone you have MS - indeed, can’t tell them so - because you haven’t been diagnosed.
Even if you were, it’s completely discretionary whether you tell prospective employers or not (there might be some very limited exceptions where A1 health is essential for safety reasons). By law, employers are not allowed to discriminate against you by reason of disability, but that doesn’t erase the fear they still might, so some people prefer to shut up about it until AFTER they land the job offer (then it will be obviously against the law if it’s suddenly withdrawn).
Not everyone with MS considers themselves disabled anyway, so if you’re asked whether you’re disabled, it might be yes OR no.
Legally, people with MS (confirmed diagnosis, I mean) are automatically covered by workplace disability legislation IF they choose to declare it - regardless how badly they’re affected. This is the single biggest reason to declare it, and get the protection. However, there’s no obligation to declare. If you don’t think of yourself as disabled, and you don’t want it on record anywhere that you are, then you don’t have to say anything. But you can’t have it both ways: choose to keep it private, but then blame the employer for not supporting you in your illness!
Finally, “relapse” and “flare-up” are used interchangeably, as far as I’m aware. Relapse is the proper medical term, but some people will talk about having an “attack” or a “flare-up”. Occasionally, though, someone might talk about a flare-up when they don’t really mean a relapse. So someone here might say: “My symptoms are really having a flare-up in this heat!” Or: “I got a flare-up after I went to the gym”. They don’t necessarily mean they’re having a proper relapse. Just that their symptoms were aggravated temporarily.
Hope this helps,