I’m don’t know how I’m not pregnant

SO and I have been ttc for about 3-4 months. I have a 4 year old and he has a 5 year old. We have sex multiple times throughout ovulation....nothing! I feel like with my first it was so easy and just happened. And now I’m here trying but it’s not happening. We’re not stressing over it, it’s kinda “if it happens it happens” but I’m just like... how am I NOT pregnant lol.

Does positions or anything like that interfere?