It’s not happening

We’ve been trying to get pregnant for 4 months now. My husband is in the military and leaves unexpectedly so it’s a hit or miss really. My test are always negative and it’s always so disappointing. My periods have never been regular so knowing my ovulation window is hard. Lately I’ve been sick to my stomach with everything I eat and some smells. I’ve had cramping and headaches. So bad we went to the ER last Wednesday. The doctor tested and it was negative, but I’m still having the cramps and feeling like I have to vomit, along with fatigue. Idk what to do and what’s going on.