Staying positive

How do you all keep positive when others around announce they are pregnant? Long story short my husband's 17 year old brother and his girlfriend are expecting a little one. It was an accident and they are both excited and nervous and my soon to be sister in law is always asking me advise about pregnancy I have 2 kids right now but it took my husband and I a very long time to get my daughter (almost 3 years) and we have been trying for #3 for 6 months already with now luck. I try so hard to be happy for her and tell her how fun it is to be pregnant and feel them move and tell her just wait till you hold the little one because I know she's nervous and I want her to be excited about being a mommy it's the most wonderful thing in the world. Am I a terrible person because sometimes I feel idk how to put it sad or maybe jealous that some people can conceive so easy and it is a long stressful process for me? And on top of it my husband's other brother also had a baby at 17 on accident that brothers wife basically throws it in my face about how easy it was for her to have a baby and if I ever try to mention the emotional struggle of trying to get pregnant she literally says "yeah I don't have that problem I can get pregnant whenever I want" sorry for the long post I don't have any sisters and just needed to vent.