Seems to me that the guy used to be in a relationship with this girl and for whatever reason he had to go away ("And I've been away for far too long it seems") but when he comes back to possibly pick things up where they left off he discovers that she's been sleeping around and picked up a crew of friends who aren't the best... ("And this new group of friends is making me, ready again to leave"). Then he basically starts asking her loaded questions about how she really feels about how she is behaving ("And will you still be feeling alright In the morning with the sun creeping through the blinds? And will you say it was a good time? And you will you tell him anything?"), followed by a warning that the guy just wants sex from her and that she is just screwing herself.
Seems to me that the guy used to be in a relationship with this girl and for whatever reason he had to go away ("And I've been away for far too long it seems") but when he comes back to possibly pick things up where they left off he discovers that she's been sleeping around and picked up a crew of friends who aren't the best... ("And this new group of friends is making me, ready again to leave"). Then he basically starts asking her loaded questions about how she really feels about how she is behaving ("And will you still be feeling alright In the morning with the sun creeping through the blinds? And will you say it was a good time? And you will you tell him anything?"), followed by a warning that the guy just wants sex from her and that she is just screwing herself.