Transmission Slips?

Hey guys, i need your help, since i bought my h3 i loved it, everything about it, somethings i would improvise, but in all i love my ride, been wanting it since it came out.

ON thursday, i went to the bank and parked it, got out, put it on reverse, and then to drive to drive off, and i felt a jerk, and the transmission slipped, i put it back on park, and back to drive, and everything was ok, it happened again on friday, saturday.

Finally today, when i was on my way dropping my kids off to my x's, it slipped on the freeway, doing about 80mph, it just sllpped completely, i have a 9 year old and a 3 year old, and it really freaked me out, i was able to pull over and exit the freeway, then it went back to gear?

any thoughts??