I felt exactly the same as you.
My son is 13 months and I had a coil put in under general, I physically couldn't open my legs for anyone, be it a professional or my husband. Childbirth violated me and terrified me.
After the coil fitting I was told it would need to be checked, by the gp, in the surgery, just me and her. So I ignored it.
2 weeks later my smear test letter came. The thought of it made me feel sick.
I have had a smear before, no issues, in scotland where the age is 20, but that was before childbirth and begging the nurse to stop and her refusing, with her hand up my fanjo.
I made a double appointment, for 3 weeks time, but on the morning, I nearly cancelled, when the appointments ran late, I nearly walked out.
But the Dr called me in, I went in and she did it. I was terrified, shaking, I think I cried a bit.... and it was fine. Yes, it hurt, well, not hurt but was uncomfortable. She check, ed the coil, did the smear and it was over in 90 seconds. Probably less. She took the speculum out and I just lay there, with my eyes shut, crying, I was so relieved.
If you want to pm me I can go through it in more detail.
I know you are worried sick and that is understandable, cancelling it isn't, this could save your life xxxx