Hi Sunnydays, as the others have suggested, I don't think the slight increase to a still rather low dose of oestradiol would have contributed to joint pains & low mood. In fact I noticed my mood was better on trials of higher dose oestrogen, but unfortunately had to revert to a 50mcg combi patch (which I absorb poorly) due to problems with Utrogestan.
It's understandable you should be feeling low if you keep getting horrible viruses & joint pain & like you I would want to do something about it.
One of the first things I noticed when I started HRT was that my joint pains disappeared. In the 2+ years I've been on it, I've also had fewer colds I think, than at any other time of my life. Immediately prior to starting HRT, I had such bad flu 2 years running that it scared me, so it's been a relief to get through the following 2 winters with only 1 or 2 minor colds.
I really understand your desire to keep your HRT dose as low as poss - I was shocked when having agreed to start HRT on the understanding it would be ultra-low dose, I discovered I had in fact been put on a medium dose patch! But as Hurdity says, 50mcg is the minimum dose licensed for osteoporosis prevention (I have osteopenia) & is standard for women post-meno.
I wonder whether you might in fact feel better on a little more oestrogen - the standard 50mcg, though this might mean more progesterone too (you didn't say how much prog you currently take), so you'd have to get that checked out first if you did want to give it a try. When I got over my shock at being on a higher dose than I'd wanted, I told myself if I was going to use HRT at all, I might as well have enough to get the full benefits. Hadn't counted on being unable to absorb the stuff well - but that's another story!
This is only me thinking out loud with my Sherlock hat on & if you are not happy with the idea of going any higher, please don't - we all have to be as comfortable as poss with what we decide for peace of mind & anything that adds to your worries will not make you feel better. I hope you manage to work out what is going on though & will soon start to feel really well.