I can't play well in real boards other than chess.com


Interesting observation.
I do much better playing OTB vs online; I make a lot fewer blunders OTB. I never really thought much of it. However, after reading your post, I'm wondering, maybe the online board is just too easy to visualize (being 2D flat and always good contrast), causing me to move too fast (causing blunders).
Solution is, change your theme to Staunton. it has 3d board and pieces, will help you to visualise..and 2nd buy or play on real chess board with real people.. or practice alone... in some days u will do better...

buy a chesset, then select a daily chess match and make all the moves on the chess board, its the best option :)

two solutions. One expensive: https://www.chess.com/forum/view/suggestions/being-able-to-use-a-dgt-board?page=5
One more affordable: https://www.indiegogo.com/projects/square-off-world-s-smartest-chess-board--2#/
I can't visualize the board in my mind easily for real chess boards. It seems to me that 3D vision is a problem for me. Any suggestion to improve considering that I get less chance to play on real board(since my friends don't play chess) ? Thanks in advance!