On the last pg before the epilogue, when Katniss says, "So after, when he whispers," ' You love me. Real or not real?' " after what exactly?

after her and peeta grow back together and she realizes that peeta is what she needs

i understand what you mean. i didnt get that part either. maybe she just maens after she was done thinking about who shed pick, or maybe after it was all over, and after they were friends again.

she said she had the same feeling thing again that she had on the beach so aka after they had SEX

I interpreted the after to mean that after they made love for the first time. And trust me, this was not because I am trying to think that way, but I really read the context and could only come to this conclusion. Here is why:
1. So after-it means that something happened.
2. The after relates to when Katniss says "on the night I felt the hunger again, the one that overtook me on the beach.
3. You need to remember that the beach was a pretty good make out session that was interrupted.
4. This time there is no interruptions, and in Katniss describing her feelings for Peeta and Gale in the ending, you can feel in the words like she is giving herself over to loving Peeta completely.
5. Peeta asking the question is the main thing that puts it over the edge for me to mean that they made love. His main point of confusion always has been where his and Katniss' relationship stands. For him to ask this question, it would have taken something pretty big. Considering that they have kissed alot, more kissing I don't think would make him believe enough to ask the question of her.
So, therefore, in conclusion, I believe he asks this question after they have made love for the first time. I may be wrong, but these are the reasons I interpreted it that way.