I married in 1986 and divorced in 1989 We had 2 children child…

Hello:
Yes, you could have a valid claim. Child support can remain payable for a child over 19 where that child cannot be financially self sufficient and withdraw from parental charge due to disability. The court would consider any income available to her and her level of expenses and if she cannot meet her reasonable expenses from her own sources of income, then child support can be payable to you , based on the income of the other parent.
If you are awarded ongoing support, then the court can also determine any retroactive amount owing. Normally they will go back three years. Longer than that usually requires some proof that the other person is blameworthy for the delay or non payment, such as having mislead you as to their income.
A lawyer is not mandatory for this but the law and procedure involved is not simple and an experienced family law lawyer will be very useful. We are not allowed to refer you to specific lawyers here due to site policies. But the BC branch of the Canadian Bar Association has a free referral service and they have information on that at their web site.
I hope this is helpful. If you have no further questions, please rate the answer positively, as otherwise the site does not credit me, even if you have paid a deposit. You can still ask follow up questions after rating though, if you wish.