Hi, welcome to Med Help. Trying to conceive is quite a journey. Been there!! It's a roller coaster of ups and downs. Excitement each month as we hope and the let down and disappointment when we get our period. I hope it all works out for you.
In truth, it helps that you've had other kids for trying to have a baby after 40 but in general, egg quantity and quality are greatly reduced once you turn 40. This is said by someone who got my babies in right under the 40 wire with two back to back pregnancies. My sister had a baby at 41, however, unassisted. So, it happens. It's just not as frequent. It's great that you are having regular periods! If you are highly intent on having a baby, my suggestion is to not delay and amp up efforts by talking about fertility options with your doctor. How can they assist you? Not sure what your budget is for this or if you have one but you may need help to conceive before time runs out. So, I'd start with your ob/gyn and see what they say you have option wise. Clomid helps a lot of women but when we are depleted in eggs due to age, it's also tricky as it can cause us to have none sooner. But they may recommend going for it. There is artificial insemination and IVF as options as well. And donor eggs. These are more expensive options but until you have all the info, you won't know what is realistic for you.
As to early symptoms, I didn't have a lot. A bit more tired? That's about it. And then after that, I had breast tenderness. One other way to know if pregnancy is possibly happening is to do a daily early morning (when you wake-- I kept a thermometer right by my bed) temperature. We go higher around when we ovulate in temperature when you chart it. The temperature starts to decrease and goes back down totally when we menstruate. If it stays high, you are possibly pregnant. The only times when I charted my temp that my temp stayed up were the two times I got positive test results. So, this is an option for you to get a little better handle on what is happening when TTC.
Anyway, I wish you the best of luck in this and hugs.