The big O

So about 2 weeks ago I masterbated and as I was about to orgasm I felt strange and I didn’t like orgasm like normal.

I felt the sensation but didn’t do the thing with my mouth or feel the pleasure, it just stopped.

Now I haven’t been horny at all the past two week and when I tried it again the same thing happened and I felt the o coming was about to cum but then it just stopped and went away before I could finish.

This has never happened before and I’m confused and slightly worried.

I also just went on the pill about 3 weeks ago

Does anyone have any ideas?