First time farmer myself ! We just bought our first cow and she is beautiful. I have found the below web site amazing.
The Merk Veterinary Manual.
It's a FREE ONLINE version updated every year!
Cow Reproduction http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/180803.htm&word=pregnant%2ccow
I did read over the material,doesn't mention "How to tell if your cow is pregnant" doesn't really seem to be much out there for us beginner farmers. So I picked up the phone and ask my pastor,he's the local cattle rancher around here,and whom we bought our cow from. I asked him how to tell if you infact have a pregnant cow,he said just watch to see if she starts making a bag and shows some sign of springing up in the next few months. You can also have a vet. come out and "bump" her (a test for pregnancy in cattle).He/she will reach in the rectum and feel for the calf through the wall. If pregnant the vet will have some recomendations for you as well.He/she can tell 40 days after breeding if she's taken or not. Its sometimes difficult to get a vet to come out so best to line one up incase you need help at calving.
Best of Luck!