TTCers!! ........ depression !!!...?

i know how you feel been trying for 9 months and in that time my brother and his girlfriend found out they are expecting, they had only been togeather 3 months and then they go and break up, dont get me wrong me im pleased for them but im never gunna be able to develop a bond because i will be constainly thinking this baby should be mine, selfish i know, iv just got to the point now where i think im just not good enough to be mum.