Just toss out the term introvert and extrovert then, they are just labels anyway. Each personality is unique and different. I used to be very social and carefree (age 13 is when it all changed for me) I became filled with anxiety and self doubt, I was experiencing unusual emotional abuse at my house and was very scared for not only myself but my close family members. My sense of "Safe" was rocked, I felt totally unsafe. I'm not sure I've ever regained that sense of safety.
Instead of feeling like other people are "safe" (such as your bf) or "unsafe" (such as strangers), try to be the "Safe person" for yourself. Try to establish that core safety within you so that you don't have to keep finding other safe people to hold onto. Try to be that person for you. That means forcing yourself to be your friend. That means paying attention to the thoughts that you're saying to yourself. That means stopping all negative self talk in your head, stopping all painful emotions that flood your body, stopping all self doubt the moment it starts happening. Easier said than done, but in order to be your new safe place, your own rock, and your own best friend, you need to nip those things in the bud when they begin. Eventually you will train yourself to feel better. Eventually you will feel safe inside yourself again.