I am sorry that your question was unanswered for long.
Were you investigated for it; blood work etc?
The laboratory testing done for absence of period (termed as secondary amenorrhea) are measurements of serum prolactin, thyrotropin, and FSH to test for hyperprolactinemia, thyroid disease, and ovarian failure, which in all likelihood has been done in your case (you mentioned blood work has been done). The causes of missed or delayed periods are;
1) Ovarian hormone dysfunctions
2) Thyroid hormone abnormalities
3) Stress, anxiety, emotional disorders
4) Sudden weight loss or gain
5) Excessive physical activity
If all the hormonal and above causes are ruled out, one of the most common types of secondary amenorrhea is functional hypothalamic amenorrhea, which by definition rules out pathologic disease. In this there is a decrease in hypothalamic gonadotropin-releasing hormone (GnRH) secretion. Multiple factors may contribute to the pathogenesis of functional hypothalamic amenorrhea, including eating disorders, exercise, and stress. However, in a few women with functional hypothalamic amenorrhea no obvious precipitating factor is evident (this might be true in your case).
Read the resource under the heading secondary amenorrhea;
There can be various causes for bleeding during intercourse;
1) Infections like chlamydia, vaginitis, cervicitis
2) Cervical dysplasia
3) Cervix growth
4) Cervical polyps
5) Vaginal yeast infection
7) Uterine polyps and fibroids
8) Injury during intercourse
A physical examination by a gynecologist and an ultrasound usually are able to determine the cause. Read the resource;
Once the cause is determined about your absence of period, treatment can be initiated. That would start the period and yo would be able to get pregnant.
Please feel free for your follow up questions.
I would be happy to assist your further, if you need any more information.