a friends struggle with IVF and resentment to me for my pregnancy

My very good friends has been struggling with fertility for 5 years and they just had their second unsuccessful round of <a href="https://glowing.com/glow-fertility-program">IVF</a> which was their last chance for a baby. I have always sympathised with them and tried to be the best support I can be as it is so very difficult for them, and although I cannot physical feel their pain I can understand it because I see it in their faces and I know they are hurting. In January I became pregnant - quite easily in fact, it was due to forgetting to take my pill just once - and now I am 25 weeks with my lovely boy. I am so excited, but my friends are not. This I can understand but it comes with other comments from them for example; "does it make you feel guilty that you got pregnant so easily and we have really been trying for a baby?" "If you're having twins you should give one of them to us" "why does god give children to the people who didn't want them?" And other such comments. The second failed <a href="https://glowing.com/glow-fertility-program">IVF</a> treatment was very recent, and still very raw. I understand the pain and the hurting but it is not my fault this has happened to them and I cannot feel guilty for carrying my own child that they are unable to. I am now being completely ignored by my friend which can be difficult as we work together. I want to find the words to say that can help them to feel better but it is hard as I know I am resented! It makes it even harder as I don't want to rub my pregnancy in my friends face but as I say we work together so I cannot really hide it or avoid her meaning I am always the constant reminder of what they cannot have. Please can I have an outside opinion on my situation?