1st time momma nerves!

Hello mommas. I am 35 and just found out yesterday I am pregnant with my first child. I am super excited because I thought it would take much longer but now that I am pregnant I am terrified of losing it. I know it’s a strong possibility and I just wanna know what I can expect if I am miscarrying. Right now I am 3w5d as best I can tell and have had mild cramping the last two days. I am also nauseated and lightheaded periodically and SO tired!! Are there signs I need to be looking for if things aren’t going well? I haven’t had any spotting as of yet. Thanks in advance for any help!