You should not presume that you are pregnant.
Your tubes have been tied. So it is most unlikely that you are pregnant as the sucess rate of
tubal ligation is more than 99%.
You have missed your period - or had very little spotting. At this age of 49 years, it is most likely because you are approaching your menopause. Initially, there is irregularity of periods before you actually caese to have menses due to menopause. When you do not get the menses for 6 months at this age, be sure that you have attained menopause.
During menopausal phase, there are many vague symptoms like
flatulence,
heartburn,
depression, hot flushes, etc. Not that all of them will be present every time.
I feel your fluttering could be due to flatulence.
I would advise you to get checked from Gynae doctor to rule out any prolapse of the reproductory organs or the rectum(Slipping down the these organs in or through the vagina) . This also can give rise to fluttering in the pelvic area. If it is there, then depending upon the extent, you may need pelvic
physiotherapy, some support or surgery.