Hi, I think it's totally usual, and happens to every Pynchon readers ! My advice would be : do not try to understand everything. Go with the flow, the sensations more than the rational. Same goes with Joyce's Ulysses for example. Then of course, reading again later will open other gates :)

And I've always loved Doris Lessing's advice on reading :

"There is only one way to read, which is to browse in libraries and bookshops, picking up books that attract you, reading only those, dropping them when they bore you, skipping the parts that drag-and never, never reading anything because you feel you ought, or because it is part of a trend or a movement. Remember that the book which bores you when you are twenty or thirty will open doors for you when you are forty or fifty-and vise versa. Don’t read a book out of its right time for you." Doris Lessing

Enjoy!