i'm not a professional but this seems like a case of denial on your family's part. perhaps especially your parents, maybe in particular your mum's but then where was your father's roles & responsibilities in all this? perhaps they didn't want to acknowledge another problem in the family on top of your brother's drug addictions? perhaps there's some generational sentiment that psychological symptoms without externally physically tangible evidence are not genuine?
perhaps she may be right that parenting is alot more difficult, scary & challenging than we might understand until we face it ourselves. is there is more to this scenario regarding your dad who was a stay-at-home dad what was his input in all of this?
in any case if she has 2 (3?) kids i'm sure she struggled, and perhaps at times it might be difficult to separate childhood imaginations from real issues, however as you grow older & these problems continue i feel it is negligent if not cruel to make a joke of your suffering.
if after all these years she still won't acknowledge it then perhaps having her do so needs not be your goal, who knows how deep her denial runs or what sub-surface forms it has latched itself onto in her psyche. don't worry about her, or your father for that matter (i'm still wondering where his role in all of this was). my feeling is not to worry about them, concern yourself with yourself.
you don't need their support now to find some guidance, it sounds like if you mention it then she'll just deflate you, so keep it to yourself. counselling is great, but i've never met a counsellor who could solve everything, they can only help unsurface issues imho the resolving is done by you.
so hunt around there are some free & subsidised counselling services you can find if cash is a problem, beware though sometimes you get what you pay for, but even if you had the best of the best my number 1 advice would be to trust yourself, what does your heart tell you, what does you gut tell you?
i've been down a similar though thankfully not as crippling path before in terms of conditions, i had every test under the sun on my stomach (I had a very thorough doctor & i took myself to him without telling the family) and in the end he ruled it was psychological. perhaps the best thing i took from conselling after that was get outside the house & do something NEW once every WEEK. start small & then become more daring, soon you should find excitement in the little new things you're doing, and pride & strength that you have done them without anyone's help. you might think you are alone but you are far from it!
good luck & remember, **trust yourself**: time has proven you were right all along, you can fix this.