What procedure is good for fixing three different prolapses, extreme urine leakage, and vagina laxity?

Based on what you've described:
You’re experiencing advanced pelvic organ prolapse involving the:

Bladder (cystocele)

Uterus (uterine prolapse)

Rectum (rectocele)
Alongside this, you also report:

Severe stress urinary incontinence

Significant vaginal laxity

Chronic pelvic pressure and pain

Heavy and prolonged menstruation

What can be done:
At this point, surgical intervention is likely the most effective and lasting solution. Based on your symptoms, here’s what a personalized surgical plan might include:

1. Pelvic Reconstructive Surgery
To repair:

Cystocele (bladder support)

Rectocele (posterior wall repair)

Uterine prolapse (can include hysterectomy or uterine suspension depending on your goals)

2. Stress Urinary Incontinence Treatment
Often addressed during the same surgery with a mid-urethral sling or other supportive techniques

3. Vaginal Tightening / Support
A vaginoplasty could be combined to restore tone, improve support, and enhance overall pelvic health

4. Management of Heavy Periods
A hysterectomy or endometrial ablation could be discussed depending on whether you're done with childbearing and your personal goals

I understand the discomfort and challenges you're facing following four vaginal births, resulting in pelvic organ prolapses including Cystocele, Uterine, and Rectocele, as well as severe stress urinary incontinence and vaginal laxity. Your symptoms, particularly the pain and discomfort in the lower abdomen, back, hips, and legs, alongside heavy and painful menstruation, certainly warrant a thorough medical evaluation and treatment.
In cases like yours, nonsurgical methods like pessaries, though beneficial for some, might not be sufficient, especially when there's significant prolapse and associated symptoms. Surgical intervention often provides a more definitive solution.
Advanced procedures such as Cystorectocele operations, which are designed to correct both the bladder (Cystocele) and rectal (Rectocele) prolapses seem to be done. This surgery aims to restore the normal anatomy and function of the pelvic organs, potentially alleviating the symptoms you've described. Additionally, addressing the urinary incontinence can be part of the surgical plan, depending on your specific condition and needs.
Regarding your menstrual issues, a comprehensive evaluation is necessary to determine the underlying cause and appropriate treatment, which might range from hormonal therapies to surgical options, depending on the diagnosis.
I would recommend a consultation with a gyneacologist to assess your condition thoroughly and discuss the best treatment options. 
Sincerely,
Dr. Mehmet Bekir ŞEN

You could be experiencing stress urinary incontinence, an overactive bladder, or a combination of both.Stress urinary incontinence is considered a medical condition and usually requires surgical intervention in a hospital setting by an experienced OB/GYN or a Urogynecologist specializing in treating pelvic floor disorders. I highly recommend reaching out to your OB/GYN as soon as possible to ensure your condition does not worsen. They'll be able to assess your situation and make sure you receive the right treatment.
A vaginoplasty procedure would address your vaginal laxity. Because vaginal laxity not a medical necessity, it would be considered an elective procedure (so insurance usually will not cover this). This is done in as an out-patient procedure with IV Sedation. I recommend you see a cosmetic gynecologist to see if you would be a good candidate for this.
Hope this helps and best of luck to you!