I'm 18- Tell my strict mom about IUD insertion?

I'm having my iud inserted tommorow. secretly. I'm 18. My parents are against premarital sex. They have full authority and power over me because I live in their household. My mom hid my bottle of ibuprofen (i bought it for the insertion) because she thought of something suspicous like me getting addicted to it (shes protective).

it's an expensive bottle of ibuprofen.

Now I don't know if I should tell her that I need it for my insertion tommorow. she won't give it to me if i dont give her a valid reason.

I have a boyfriend of 4 months- lost my vcard to him and we had a pregnancy scare but we love each other. My parents are strongly against me doing anything sexual with him.

i'm scared if they tell me, i wont be able to go to my appointment tommorow because they wouldnt let me.