Is it possible to get pregnant while nursing? Possibly TMI

Do you think it makes it a little more difficult? I’m over 35 and I nurse my toddler still pretty much on demand you can say. If she is visiting away I don’t pump or nurse her. I just nurse when I see her again. About a week ago I had sex and this time he fully came inside. He usually pulls out. And sometimes he will say a little got in but I never get pregnant. Well I thought surely I was going to get pregnant this time. I was about a week and some days before I was expecting my period so I guess I wasn’t ovulating but I didn’t know that mattered. I seemed to get pregnant with ease before but I guess I never really paid attention to any timing. Well I have been feeling like I was pregnant ever since. My sense of smell was a little stronger. I’ve been more tired. I was peeing more often. My nipples felt more sensitive. I was mildly nauseous. More “frisky” I just knew I was pregnant. I ordered some prenatals last night to start early. I stopped drinking. I got a pregnancy test last night and was going to wait a couple more days to use but today my period started. And I was so shocked! I just knew I was pregnant and I guess I’m not. Well I’m not. Is it because I wasn’t ovulating. Does that really play a role? Because if so why do people have sex often when TTC? Or could my nursing be affecting anything? Ugh, he never fully ejaculates inside of me and when he did I felt like he wanted it as much as me and it was gonna happen but I guess the timing was off or idk. I’m usually very fertile. I hope to have another baby by 38.