Hello there dear @Jimbo165, you do make me smile even as you share something that’s not so funny! It really seems like that combo of medicines does a number on you every fortnight. I’d say it’s really helpful to notice these patterns as we can then tell our specialists who should be keeping note 
May I ask, when you say you develop aches and discomfort, is it like bad flu symptoms or something else? It doesn’t fun at all and I can’t help but wish that your specialists could help with those symptoms. As they’re so frequent and follow your treatments it would make sense that your haematologist would want to minimise them. What do they say?
I hope you don’t mind @Jimbo165 but I’m going to ask the @BloodCancerUK_Nurses if they have any suggestions about dealing with those aches and discomfort and ways to reduce them, I hate knowing you go through this every 2 weeks. Like you say, maybe it’s a pretty unique response as you take those 2 different medicines for Essential thrombocythemia ('ET') with a CAL-R gene mutation. Perhaps there’s something that might help.
Have you tried searching the forum for others taking both hydroxyurea and Pegasys or variations of your diagnosis? Let’s see if anyone’s posted something… I know dear @Lucky has tried a few of our treatments and perhaps wouldn’t mind sharing how it was, but no pressure Lucky.
This thread where you’ve commented might have some pearls of wisdom within the many posts: Experiences with Pegasys for ET
Some discussion of CAL-R and Myeloproliferative neoplasms ('MPN') in this thread: ET or PV?
Hopefully you’ll find or receive some tips that will help @Jimbo165. Do consider letting your specialist know just how rubbish your medicines make you feel every 2 weeks.