Help me find a book

The book has multiple different stories. One has a man and a girl sitting in a car maybe sharing milkshakes? In the rain and go swimming. I’m pretty sure one of them was gonna die, at 16-19. Another story in the book had some sort of alien creature that I believe was gray and would attach itself to your neck. The book was grade 6-8 reading level. I know it’s not much info but I would be very grateful if this rings a bell for someone. Thanks

by Designer-Spinach8736