@mikimouse you don’t need to go to the doctor now. What you need is at least 20-30 minutes of foreplay focussed on you and your clit to get you ready for penetration in the first place. Maybe use lube too (water based is recommended). You can’t have sex if your body isn’t prepared properly. It takes time, foreplay is a very important part of sex.
If you use your birth control correctly then you don’t need plan B. Taking plan B unnecessarily is not good for you at all. It has a massive amount of hormones that will affect you for weeks if not months.
If you do not fully trust your birth control then you and your partner should both carry condoms just in case another spur of the moment occurring again.