You describe your partner’s penis as “smaller than most,” and wonder how to enhance your intimacy--especially intercourse. A reminder, first, that foreplay, which is helpful to both your arousal and lubrication, is an often undervalued part of intimacy. Assuming that you’re taking full advantage of what that “warm-up” has to offer, there are additional things you can try.
You can try using an internal vibrator, which you or he can use as part of your play together to provide the feeling of fullness some women prefer to experience orgasm. Both the Celesse and the Gigi2 are specially shaped for G-spot stimulation, if that’s an issue for you.
And I do hope that both you and your partner are open to the reality that for humans, sexual pleasure takes many forms! With some exploration, I’m sure you can assure that you’re both satisfied--and comfortable with yourselves.
While this isn’t common, it does happen. It’s usually attributed to semen. Semen contains prostaglandins (PGs), and PGs cause uterine contractions or cramping.
You can test this theory by using a condom with intercourse a couple of times to see if you still experience the cramping. The condom keeps the semen from the cervix, which should reduce reaction. You can also use withdrawal, removing the penis before ejaculation.
You can also try taking ibuprofen or Aleve before intercourse; these are anti-prostaglandin medications that can ease the cramping as well.
I hope one of these approaches works!
What you describe—clear, odorless fluid released when the "right spot deep inside" is stimulated—is classic "female ejaculation." The fluid comes from the Skenes glands located along the front (anterior) wall of the vagina; the Skenes gland is roughly comparable to the prostate gland in men. For some women, direct stimulation of that spot on the vaginal wall releases the fluids from that gland.
Not all women experience this, but it's certainly noticeable for women who do! It's not, though, either unusual or a cause for concern.
Estimates say that up to a fifth of heterosexual couples have anal intercourse at least intermittently, more rarely exclusively.
The risk of sexually transmitted infections is the same or perhaps higher with anal than with vaginal penetration. There's more likelihood of trauma, since anal intercourse requires complete relaxation of the rectal sphincter muscles before penetration. Trauma or injury to those muscles can lead to loss of muscle tone or control. That makes this form of intimacy not entirely "safe," but, more importantly, consent freely given by both partners is an essential feature of sexual activity in a loving relationship.
You asked whether this was a new phenomenon and whether you were "too old" to adapt! I don’t think it's new (or, at less than 20 percent, a phenomenon), but our notions about sexuality and what's "typical" or even erotic are very complicated and influenced by many factors. You may never become comfortable with this form of intimacy, but you are never too old to explore options and be open to new sexual techniques.