Female in heat

First.… appt to get spayed the end of January

Had a tomcat show up, he set off my female to go into heat.

I have only had males for the last 20 years, so I can't remember if this is normal or not.

My poor female sounds like she is in pain when she is in heat. She will cry out and her abdominal area will tense up and she looks like she is pushing. Basically reminds me of contractions I had when I was in labor. She only does this when she is in heat. Is being in heat painful? Do they have cramps? Another thing she does is get in the litter box and strain very hard and instead of passing stool, she passes gas. She is NOT constipated and she does NOT have a UTI.

I am wondering what the typical, normal actions of heat are? Besides the butt in the air, etc. I am NOT asking for medical advice, just asking for the usual signs/symptoms of a normal heat cycle