Exercise advice

Hi, Im new to the forum. Were hoping to conceive a girl after 2 boys (7 & 5). Prior to trying for #3 I was doing a lot of running & biking & have run 2 marathons in the last year. I eased it off at the start of summer as felt like I needed a break, then had a few weeks of no exercise as we were traveling in Asia. During this time we conceived and because I was tired & feeling a bit rough I didnt run again, just did a few gentle pregnancy dvds. Unfortunately, I have just miscarried at 9 weeks. We are keen to try again soon, but not sure whether it is best to get back into the cardio 5 times a week or to leave it as too late to have an effect?
We did 2 attempts at o-4 (7 day abstain) and o+12 before but am thinking e4d as dont really know when ill Ovulate. Am nervous about cranberry/aspirin/abstain because of the mc and our ages. I am 39, dh is 38.
I have been on pregnacare & dh has been taking berocca but will stop these and I will just take folate. Am considering cal-mag but not sure if this sways?
Also considering Sudafed 2hrs before?
Were both happy to drink coffee & alcohol 😊
Ive put on a bit of weight the last few month so am going to try and skip breakfast & keep cals under 1800, but still feel like I need iron & protein as pretty drained after the mc.
Any advice on the exercise, or general tips on a gentle sway after miscarrying would be appreciated.