@Roberta,
The ability to understand subject matter doesn't necessarily translate equally for all in all areas. Think of this is a multi-sided but not symmetrical shape. The 'flat spot' on this shape for you happens to be math. Some of us 'smarties' have flat-spots in other areas. The fact that you have this non-affinity is by no means a reflection of your IQ.
Call this math area your non-comfort zone. It's not that you aren't capable, you just didn't learn to excel. Then, due to the discomfort ('cause you excelled in other areas), you avoided it. And like any other brain activity when not exercised, those 'math muscles' atrophied.
If you were highly motivated or rewarded enough and taught math in a way you liked, you could learn math; however, it might not possibly be the advanced calculus or some of the extremely esoteric areas. With the right training, you could go pretty far, but you would have to unlearn the anxiety you associate with math.
Know-it-all academics call some folks with a math deficit as having math-anxiety. Back when we were kids, society often imposed a pre-conditioning on young ladies as they went from grammar to junior high and the on to high school. I noticed while growing up that girls would be socially conditioned away from excelling at math. Somehow math wasn't 'pink and cuddly' enough
Math teachers were in on this conspiracy and would focus their energy on the boys and would consciously or unconsciously discourage the girls. This translated to very few girls in the early-'70s going into engineering and the some of the sciences. During the mid-70s the trend faded a bit but the damage was already done.
Women and Advanced Math
Mavericks who ignored the conditioning did extraordinarily well, encouraged by role models such as Madam Curie, and computer pioneers like Ada Lovelace (considered the world's first programmer), whom they named the Ada programming language after.
The famous math whiz and computer expert Grace Hopper received graduate degree in 1930 and was the first programmer for the Mark I Calculator, known as the "Mother of COBOL". In her role as Rear Admiral with the Navy in WW II, she was quite instrumental in early years of computer industry. In her later years she was a senior consultant to the computer industry and at Digital Equipment Corp (DEC) until she was 85 .