Technically, you can do that. However, the more you do that, the harder it will become and you may need to eventually be able to respond to the following questions or they may not let you in:
1) Why are you coming back so soon?
2) Why you couldn't do what you needed to do during the last trip?
3) How will you be supporting yourself for this additional time since you are not allowed to work?
4) What STRONG ties do you have to your home country to ensure that you will go back?
5) What preparations have you made to go back?
If they are not satisfied with that, they could deny you entry into the U.S. So you have to be prepared. Also, here is a link that I can give you of things that you can have with you to prove non-immigrant intent and strong ties to your country. Here is the link:
Once you are married to the U.S. Citizen, it will become much harder. Why? Because apart from every non-U.S. Citizen automatically be assumed to be a potential immigrant (which is why you have to prove that you are not), once a person is married to a U.S. Citizen, they automatically assume that they want to enter on a Visa Waiver or B-2 just because they do not want to wait stuck outside the 9 months or more processing time to apply for an immigrant visa. So again, it will be much harder, but if you have strong proof of non-immigrant intent and strong ties to your home, then technically it is possible.
It is a dangerous situation with risks, but if you are eventually denied, you can apply for a B-2 and try again, or you can have your spouse finally apply for you to get an immigrant visa, then get your Residency, and then do as I originally explained and get a Re-Entry Permit to come in and out with almost no issues like you would have now with the questioning and proof. I was just trying to make it easier on you.
Please let me know if you have additional questions and please do not forget to rate my service to you positively (not the state of the law) as that is the only way that I can get credit for my assistance. Even after you rate the service, I can still answer additional questions for you without additional charge. And don't forget that bonuses are always appreciated! Thank you.