I was coming to the US on a visa waiver for the third time now to visit my boyfriend who is an US Citizen. Everytime I stayed here for about 85 days and then went back to Germany. I entered the US again in August on a visa waiver, when my boyfriend asked me to marry him when he picked me up from the airport. We got married 2 weeks later and we already filled out all the paperwork and I also went through the medical exam (which was on our wedding day). Now a laywer told us, that it would be better for me to go back home again (!)and file the K3 visa, because we got married too quick. But why should I do this? Is there anything wrong or illegal that we've done?

I think what your attorney is concerned about is the fact that the USCIS (the new name for the INS) could deny your residency application based on fraud. The USCIS could determine that you fraudulently entered the country as a tourist when you in fact planned to get married and then apply for residency. You could then face deportation from the US unless your husband (or a parent who is a US citizen or lawful permanent resident) can show that he would suffer extreme hardship if you are not allowed to remain in the US. Hardship waivers can be very difficult to obtain as mere separation alone does not necessarily constitute hardship.

It is very difficult to predict how a case like yours will be treated. It depends in large part on the USCIS office processing your application. You should discuss your options very carefully with your attorney. Going the K-3 route obviously is the safest route, but you should have all of the information at your disposal in order to make a decision.