guys asking for numbers/instagram—how to ward off guys safely while also making my boyfriend feel comfortable?

whenever a guy asks for my instagram/phone number i give it to him/give him a random number— but i always immediately block after they are out of my sight. understandably, my boyfriend feels upset because im making myself seem available to men, however, im terrified of saying no in case of their reaction. ive moved here about a year ago, and i’ve already been sexually assaulted from a random one off interaction with a man, so im definitely keeping my guard up— how can i stay safe while also saying no?