Two things came to mind when I read your question.
If you do not tell your partner, you are setting up a precedent of keeping secrets. If you are interested in developing a long term relationship, you may not want to do that.
Being able to orgasm requires that you allow feelings to flow through your body. When that is not happening, you may be having issues going on at an emotional level that are showing up in your inability to orgasm.
To get over the edge, you may want to consider this: Your mind and body are not separate. Issues of the mind are revealed and expressed in the body. There is a very good chance that there is some emotion that you are managing by tensing the muscles of your pelvic region. This will inevitably affect your ability to orgasm. In order to do so, you will need to address the emotions that are locked up in your tense muscles.
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