My bf's sister is against us ttc

So the other day my bf was on the phone with his younger sister (she's 26 and my bf is 27) and basically they were just catching up with each other's lives, she lives in another state with the rest of my bf's family (parents, siblings). So they were just talking about her since she had recently been on vacation and they were talking about her trip. She then asked my bf what's been going on with us and well he told her a few things and towards the end he added on "hey well I recently went for a sperm analysis" and she immediately answered "what the hell don't tell me you guys are trying to get pregnant" she was on speaker so I was basically listening to their whole conversation. He then told her how all this years we've been together we never used protection or birth control so it was kind of odd we still haven't gotten pregnant. She then added "OMG so you are trying to have a baby" (she sounded pretty mad at this point) my boyfriend told her "Yes ! We are." She made a big sigh and said "wow you're stupid" , "why do you wanna have a baby?" "What's the rush?" . To be honest at this point I felt like screaming. I got up and walked away, a little back up story I have Endometriosis and we just found out my bf has low sperm. We've been ttc for 3 years now and still nothing. Her saying "what's the rush?" Really pissed me off because in reality we have been trying for 3 years and I'm still not pregnant. She basically told us we're stupid for trying to get pregnant and that we shouldn't be worrying about that at the moment. Getting pregnant is not as easy for some as it is to others and unfortunately for my bf and I has been a very difficult situation, we've cried and had thought of

just giving up. My bf explained to her our situation of us struggling to conceive and all she said was "oh ok yea it's not your time". She has been a real bitch with us regarding this matter.