Student Visa (F1, F2, M1, M2)

I am a dentist in India and my parents and brother are also dentists. I have been working in my father's dental clinic for past 5 years. I got a tourist visa in 2017. I travelled to US on that visa in 2017 - for 20 days and then in 2018 after my marriage for 5 and a half months. I got married in 2018 January. At that time I was volunteering in a research project involving oral cancers in India. Our project got selected for a presentation in a conference in USA, so I did not have enough time to get my visa changed to a dependent visa at that time, hence I travelled on the tourist visa itself, presented the work in a 2 day conference and then stayed with my husband for roughly 5 and a half months. Then, I came back to India and have been here since last 1 and a half year doing my work in the clinic. Now, I managed my work accordingly that I could take out time for 1 year, so I wanted to change my visa to dependent visa (F2). Here is how my interview went:

VO: Pass me your passport and I20
I gave it
VO: So, your husband is studying there?
Me: Actually, he graduated last year and currently he is on his....(before I could finish my sentence, VO, finished my sentence saying he is on his OPT)
Me: Yes
VO: Where is he working?
Me: told him the company name
VO: When did he go to U.S.?
Me: told him
VO: I can see you spent 6 months in USA last time
Me: Yes, that happened right after our marriage, I was invited for a presentation in a conference there, so did not have enough time to change my visa to a dependent visa, so after the presentation, I stayed with my husband for 5-51/2 months.
VO: Were you working at that time?
Me: No
VO: Where were you working at that time?
Me: Sir, I was not working at that time. I was with my husband.
VO: Was your employer okay with you leaving work for 6 months?
Me: Sir, I am a dentist and I work at my father's clinic, so before leaving I managed my patient appointments accordingly so that I could take out time for 6 months and after coming back I have been immersed in work for the last 1 and a half year. Now again I have scheduled my patients in a way so that I can take out 1 year now.
VO: So your employer had no problem with you leaving work?
Me: Sir, I am a dentist and I work with my father in his clinic.
VO: Please give me a moment.....
VO gets up, goes to the back and talks to someone and then takes photocopy of my passport, comes back and starts typing something on his computer. He typed for almost 15 minutes and then
Unfortunately, I cannot give you visa at this moment and I have also cancelled your tourist visa
I was so shocked and I could just utter: Sir, what happened? Can you please tell me the reason?
VO: I have given you the slip

It was a generic 214(b) slip. For few moments I could not understand what just happened? My concern is I never overstayed at my visitor visa, yes it was a little over 5 months but it did not exceed 6 months and then I never did any kind of work in US, so why was he asking me that. I am a dentist, that is the only work I know. The 214 slip talks about intent. The fact that I came back on time last year and have been working here for past 1 and a half year in India, itself shows I have ties here. Even now when I am planning to stay for more than 6 months with my husband, I came here to get my visa changed. So, where is my intent wrong, I fail to understand.

Anyway, I dont know what to do next. Does cancellation mean I can never apply for any visa in any category. What should be done? Did anyone face similar situation? Can anyone help me or guide me what should I do next?