I think its either not acid, or a very low dose. Now your tollerance will be pretty high if it is acid so taking more will most likely just make it last longer, although sometimes if you are almost on the verge of tripping a little more can change the experience to a full blown psychedelic experience.
By the way, LSD is very much different than MDMA, maybe what you have is DOx, it is commonly passed off as acid, but has more of a mdma/amphetamine tinge...
Had half a sugar cube at 10pm. Two hours later, nothing. Then suddenly chatting to someone felt incredibly horny. Since then its felt exactly like MDMA. Buzzy euphoria, but less intense. I am wondering if anything visual is gonna happen now or should I risk the other half?
IME, nothing kills a trip like sitting infront of a computer doing the same things you always do.