During interview and observations I asked questions keeping in mind themes. After that I analysed and data on the basis of themes. Is it content or thematic analysis?
If you've started with themes - this doesn't fit with our reflexive approach to thematic analysis as themes are built from codes and developed later in the analytic process. However what you've done might fit with code book versions of TA - like template analysis or framework analysis - or some coding reliability versions. Check out our TA website for references on all of these: https://www.psych.auckland.ac.nz/en/about/thematic-analysis.html
Farzana Khan - Not clear what research methods are you using under qualitative research? Why do you need to generate themes on the basis of your research question? What are the basis for your approach?
Stating the results in terms of themes is one of the most common formats in qualitative research, so that would match either thematic analysis or content analysis. The best known approach to thematic analysis is Braun and Clarke, (2006), is you want to use that label for your work, you should see how well your own procedures match what they recommend.
FYI, the citation above from Uzair Iqbal Janjua is to Vaismoradi et al. (2013).
Braun and Clarke distinguish between 'domain summaries,' which they describe as 'summaries of what participants said in relation to a particular topic or data collection question' and themes, which are developed from the data by the researcher(s) and are characterized by a 'central organising concept.' So if someone were to conduct interviews with themes already in mind, that would suggest that they were not doing reflexive TA as Braun and Clarke describe it.
It sounds like you probably followed Braun and Clarke according to the 2006 version of their work, but as Mark Harrison notes, they have updated their approach since then.
Still, I question whether they would object to conducting "interviews with themes already in mind" because they are largely silent about how the interviewing portion of the research process affects the later development of themes. Further, their argument for what they now term "reflexive thematic analysis" is stated in terms of whether or not there was a codebook in place prior to the thematic analysis process.
Bottom line: Cite Braun and Clarke (2006) as the basis for you analysis and join the tens of thousands who have done the same.