I am 22 year old, I want to take a science class, I feel like it is too late. Do you think is it too late to apply college course?

I was in mainstream school from year 7- 10(up till half term October) and I went to a special needs school from year 10- end of year 11 (I've got ASD, I was bullied and new special needs teacher at the time transferred me into special needs school). When I was in special needs school I didnt learn anything much and I was only learning stuff that I have already learned when I was in year 7. In mainstream school I learned a lot, I struggled to understand and focus. 

I am now realising that I haven't learned much when I was in special needs school and I feel really guilty, I wish I should learn more stuff as I was in mainstream school.

I just wanted to be a normal youth but I feel like I am not a youth no more, I feel thats it and I cant learn anything. 

I don't like being delayed, I just want to do it until it is completed.