I'm a 31 year old male. When I get aroused, instead of erections, I've begun to just get a tingling sensation between the anus and scrotum.

See a urologist. May have an issue with erectile dysfunction that could mean vascular or nerve pathologies. May want to visit urologist for further evaluation.
Arousal. The nerves which enervate the penis are also involved in sensation in the surrounding areas of the perineum. Sexual arousal may result in sensations in those areas close by just as they may also result in erection.