I am feeling low & feel like giving up TTC

I am 27 my hubby is 28. We are both heathy no problems. We had our 2 year old son easily after 3 months. We are TCC since 5 months and no luck. I have used ovulation kits and concieve plus nothing helps. I am taking angus cactus and using preseed now. My two closest friends are pregnant now and I feel left out and I feel I dont fit in anymore. One friend is having her third baby and the other is her first baby. It is bittersweet I am so happy for them. I am over the moon but deep down I am sad and feeling depressed. I feel like giving up because every time I get excited about having a second baby my period comes. I am fed up of trying to have another baby. I guess I am unlucky. My friends keep telling to have another one and I have to lie and say I dont want a baby right now.