If you do leak even though you are wearing, this could be due to various causes.

1. The cup is not unfolded properly and therefore does not draw a vacuum. You can try a different folding technique and reinsert it. After insertion, turn the cup 360 degrees at the base (above the stem) to check that it is really sitting properly.
2. The cup is touching your cervix. The cup should encase the cervix, if it touches it, it might cause a blockage. It may be that the cup is missing your cervix and that it is leaking past it.
3. In people with a low uterus, the cervix itself could be in the cup. As a result, the cup has less capacity, and you have to empty the cup more often. So, check if your cup is not too long and check how deep your cervix is.