Struggling TTC

So I am 21 and my boyfriend of 3 years is 25 and we decided back in June that we wanted to start trying for a baby. So at the end of July I got my IUD our and started trying from there. I started tracking my periods since I haven’t had one while I had my IUD. We started tracking sex and trying to do it on the most important days. And each month we have gotten a negative and continue to be crushed. Last month I was 4 days late and then got my period and this month I am now a week late and still am getting a negative. Now I will add we both work pretty stressful jobs, he’s a tire/diesel mechanic and I work for American Airlines scheduling our flights and crews which gets very stressful at times. Just trying to get some advice on what we can do to up our chances and try and help us make the family we want so badly. Thanks in advance! ❤️