Staarkali, Your major problem is how should we translate "I've just jumped".What about 天啊，我跳下去才发现没带降落伞.Although it's not a word-to-word translation.
Assuming the case is that you've just jumped out of a helicopter and found out that you didn't bring along your parachute,If so, I think the use of 跳过 is inapproriate because it gives the impression of jumping over something (or maybe you mean 跳过头？) rather than a downward action.
And I don't know if it was your typo or maybe it was not. Anyway, note that 可我 and 我可 are used differently. If I am not mistaken， I believe you mean 可我(a shorter version of 可是我).
Your choice of words "我可" suggests something different, and it doesn't seem to fit the context.