Cramping after intercourse

I found out that I’m pregnant few days ago, now I’m almost four weeks, last night my hubby and I had intercourse, he was very gentle though because he was scared to hurt the baby. I had minor cramps afterwards and this morning I spotted once it was pink thin string, I called my doctor’s office and the nurse told me not to have intercourse until my first appt which is over 3 weeks from today. It kinda sounds ridiculous to me, what do you ladies think?