Your lining at this point of pregnancy has nothing to do with Clomid. The lining was thin because the pregnancy was sadly not working out and that is just how your body ends things - reducing hormone levels which causes the lining to thin, bleeding begins
Re time on diet, the trouble is, time is not our friend here. While we have had good results with conception at 41, it really starts to drop off steeply at 42/43 and beyond that point, we've had very few successful pregnancies 44 and up (very, very few, despite several people still trying at this age). Just like with the Clomid, this is an individual thing. Some people are staying fertile into their 42nd or even 43rd year, others start having trouble conceiving 38-40 or even younger. Overall, I am observing the line of demarkation to really be 41 and so I don't think it's wise to take time to go back on diet for a certain number of weeks. Most still make good eggs at 41-43, but they become fewer and fewer. So you may be making 6 good eggs a year or 4 or 3 or 2 or maybe even just one. For all we know a)it will take a few months for you to conceive anyway OR b)by waiting, you may miss one or more of those good eggs and then end up into a set of months where you run through some eggs that are not genetically sound. We just can't know, and so I really hesitate to have any 41 year old wait any given amount of time after a loss to try again. Goldie the Golden Egg may be the next egg that shows up.
If you go back on Clomid I really strongly urge you not to do one attempt. I really think even without Clomid you need to consider not doing one attempt and going straight to e4d.