I married US citizen during my stay, but didn't apply for a green card. Is the short amount of time between two entry going to be a problem? Or does marrying a US citizen makes my B2 visa invalid? Thanks!
The marriage does not invalidate your B2 but if questioned at the point of entry regarding the frequent trips, you will have to tell the truth. If the officer suspects that you have the intent to remain permanently, I wouldn't be surprised if he/she sends you back home.
This answer is for informational purposes only and should not be construed as legal advice.
It does not make your B2 invalid; however, you may not be allowed to return on your tourist visa. I would highly recommend seeing an immigration attorney to get a greencard NOW.