thanx for sharing your concern,
root canal treatment
is done to save your tooth , in this treatment, tooth as whole structure is saved by just entering into the pulp canal, cleaning it, shaping the canal and finally obturating it aseptically.which you have already undergone.
after that a suitable crown is placed on that, so that it helps in functional and para functional movements of teeth, at the same time bearing the load, while chewing and transmitting the same effectively downwards to the periodontium
as you have mentioned your dentist
has taken xray which appears normal to him. that means your root canal treatment is absolutely fine.
your problem lies with the supporting structures called periodontium, which holds the teeth in place (endoperio lesion).
A problem in supporting structures can make the teeth loose (mobile) and finally fall off.
so this is equally important.
any infection anywhere in tooth or in supporting structures is clearly visible in xrays.
your dentist says, to keep an eye on gums that is because he wants to check if there is any further progression in infection in gums. as you already have bleeding, pocket and pus. if this progress , deep scaling and curretage has to be carried out to restore the the periodontal health.
for now,you can do warm saline rinses , use chlore hexidine mouthwash 2% and maintain very good oral hygiene
this should help