When I was in treatment for Lyme, I was taking antibiotics similar to yours and also took magnesium (Mg) supplements, which my Lyme doc was indifferent to -- he's a great doc, but not focused on anything but killing Lyme. His view was that eating a so-called 'balanced diet' was enough.
That was fine with me, but I did enough reading to find reputable posts and articles that the muscle aches, twitches and cramps I was having (when I first was on antibiotics to kill the Lyme) could well be caused by the Lyme bacteria using up Mg from my body, since the Lyme bugs have a need for Mg in their reproductive process.
I also read that the American diet is often inadequate in Mg, so I started taking good quality Mg supplements ... I read that any variety of Mg ending in '-ate' was easier for the human body to digest, and I tried several varieties. For any supplement, a good quality brand is important imo (but I also take 'gummy bear' vitamins, so I'm not fanatic about this stuff).
My favorite formulation of Mg (after trying several) is Mg malate, but you might want to look at what's on the shelf at the pharmacy or online and try different ones, like Mg citrate, aspartate, and some other fomulations. I don't know what makes the difference among the varieties, and it may be due to personal body chemistry.
One thing I decided NOT to take was a combo pill of Mg and calcium. Those are commonly seen on drugstore shelves, but it just didn't work for me, and the quality of the ones I was finding were rather low. Nothing against drugstores: it's a good-quality brand I care about.
I do have a favorite manufacturer's brand of Mg that I still take every day, tho Lyme is long gone from my life. I don't post the brand I like on screen here, because it's just a personal preference that has worked well for me and is good quality, reasonably priced, and easy to get through mail order. If you'd like to know the brand, let me know by responding to this email, and I can send you a 'private message' through this site -- go to the top of this screen, and in the blue bar at the top, hover your mouse over 'My MedHelp' and a dropdown menu will have 'inbox' as an option. That's where private messages arrive. It keeps everyone's identity private, both sender and recipient. Other than mail order, you can also check with your local drugstore or 'big box' store.
[Just changed my mind: rather than make you send me a message, I'll just send you a private message with the brand I like, so look in your inbox on this site in a few minutes after I send this, go to the blue bar at the top of the screen and click on 'My MedHelp.' fwiw.]
You might find some supplements that work better for you, so it's just a suggestion.
So ... that's my story! Sorry to run on here. Hope you feel better soon. And be sure to tell your Lyme doc about the supplements you take ... My doc, as great as he is, was *totally* not interested in vitamins and supps, but I always make a short list of all current meds and vitamins and supplements I am taking and hand it to the doc at the start of each appointment, just so the doc is up to speed with it all.
Yes, I also get cramping in my lower legs and feet, mostly at night. Usually it's pretty light but I've had a couple ugly episodes. I take magnesium malate and I try to occasionally do a foot soak with epsom salts (which are magnesium and absorbed through the skin, besides which it feels great!). Just be aware that magnesium can interfere with pharmaceutical antibiotics so take it a few hours away from them
I agree with grdner's comments above.