#1 - "on a trip"
#2 - "being on a trip"
The extra word "being" that distinguishes #2 from #1 gives #2 a power that #1 does not possess: the power to act as a noun. So, for example, you can say
"I love being on a trip"
but you cannot say
"I love on a trip"
to indicate that you love trips.
On the other hand, in most situations where #1 is used, you can also use #2. You should not do this though, unnecessarily, because it produces correct, but awkward sentences. For example:
"I am currently on a trip" (good sentence)
"I am currently being on a trip" (grammatical, but awkward).