unfortunately, treatment times for longstanding infections with lyme are typically much longer than 4-6weeks
some discuss an expectation of at least a month for each year of illness
in my experience this estimate / rule of thumb is on the lower side
each case tends to be quite individual with a very wide range of manifestations and treatment courses
some people do improve sooner than this - and at least a positive response gives confidence you are on the right track - which is a huge positive with such a difficult to diagnose illness as this
LLMD's who treat chronic cases tend to talk in terms of 12montsh to 2years of treatment
they also tend to use multiple antibiotic combinations - as apposed to monotherapy.
this document published by ILADS ( The international Lyme and Associated Diseases Society - the organisation that educates and represents Lyme literate MD's ) gives a better overview of Lyme diagnosis and treatment than any of the CDC, ECDC, or IDSA literature - which appears to be heavily biased towards downplaying lyme, presenting it as an easily diagnosed and easily treated rare disease and denying chronic lyme all together and generally muddying the waters around the scale of the problem and its resistance to treatment.
https://lymediseaseassociation.org/wp-content/uploads/2009/08/burrguide200810.pdfNote - there is a newer published official guideline also available here -
https://lymediseaseassociation.org/lyme-tbd/medical/treatment-guidelines/but the background and knowledge of the disease and its manifestations provided by the Burrascano's document is invaluable
we cannot know the reasons for this deep division in the medical community - but the research done in the last 20 years speaks for itself in terms of which side is most closely following the science - and which side is misrepresenting it to suit their agenda.
i mention this because - if you have been ill with lyme for more than 6 months then you have chronic lyme - and will need to be very careful which resources you use to understand your condition and guide treatment decisions - as the two sides of the divide give very different views.
in addition, co-infections are common ( perhaps present in most if not all chronic lyme cases )
in your case with the blood work abnormalities leaning towards high RBC turnover - and the chronic gastritis you mention - both are signs consistent with bartonella ( ref Burrascano's comments in the above document that indicate that Bartonella is the 2nd most common cause of gastritis after H. Pylori ) - so in your shoes i would be keen to address that - either by testing to confirm its presence - or via the antibiotic regimen chosen to treat it.
again - unfortunately, serologic testing is v poor for bartonella at general labs - worse than Lyme testing - due to strange things it does to the host immune system.
Better tests are available at specialists labs - like Galaxy Diagnostics - but they are very expensive
in terms of information resources - the best primer on bartonella is available here - its presented by the worlds most eminent researcher on bartonella Ed Breitschwerdt - and the best known conventional medicine doctor who treats it clinically in the USA.
https://www.youtube.com/watch?v=njywmmpjikueverything Breitschwerdt publishes is meticulous as he is at the top of his field - and very much aware of the schism and resistance amongst his peers - so his papers on bartonella are also amongst the best out there.
hope its of some help