Yes, it’s perfectly normal. Just as long as you don’t have severe cramping and bleeding.

this is from http://www.iampregnant.com a very very good site

Back pain is a common complaint amongst pregnant women because of the increased stress caused to the body by carrying a baby as well as the various anatomical changes that the body undergoes during this time. The growth of the baby causes a change in the position of the internal organs and increases the stress on the lower spine, leading to an increased level of discomfort in the lower back. In addition, the hormone progesterone which relaxes the muscles as well as the change in your focal centre of gravity increases the problem of back pain during pregnancy. If you have suffered from back injuries or problems before pregnancy, the problem is aggravated even more during pregnancy and thus adequate measures should be taken to alleviate the pain as much as possible.

The most crucial factor in back pain is the posture, so it is important to stand up and sit straight and tall. Avoid sitting for long periods and even when you must sit, make sure your seat is comfortable and firm and cushion your lumbar area with a soft pillow. Always take frequent breaks while sitting and walk around intermittently to exercise your lower limbs and get relax the back muscles. When you are lying down, cushion your back using soft pillows and lie straight keeping your thighs parallel to each other. Roll over to the side slowly, pushing yourself up into a sitting position before getting out of bed. This will go a long way in alleviating the back ache. Apart from this, you should avoid sleeping face down, lifting heavy objects and wearing heels during pregnancy. It is advisable to get some help with the house work and to get regular massages with herbal oils such as almond oil, mint oil and eucalyptus oil to ease the tension in the lower back muscles and get some relief from the pain. Taking a warm bath with essential oils such as lavender, ylang ylang or marjoram helps by relaxing the back muscles and soothing the tension in the lower back. However it is important not to use more than 2 to 3 drops of the essential oil each time and to avoid lavender in the first trimester since it can stimulate contractions. Physical therapy is often recommended in cases of extreme back pain. It is also important to exercise regularly with the consultation of your gynecologist who can suggest exercises that will alleviate and keep at bay the back pain. Finally, homeopathic medicines such as Sepia and Nux Vomica help in reducing the back pain, but they should be consumed after consulting a doctor.