I am a married person with two kids; my wife has put the spiral to postpone getting more kids at this time. This leads to the increase of the menstruating period (10 days or more of blood). Sometimes this sometimes lead me to perform masturbation by myself, I want to know is this Halal or Haram, though this has no effect on my sexual life with my wife?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Fixing a spiral in the vagina is forbidden unless there is a real necessity for doing so, because the operation itself requires a close look at the woman's private parts and this is lawful only for her husband. Even fellow women - under normal circumstances - are not allowed to look at this very part.
All the scholars are agreed that it is forbidden for the woman to expose her private parts to any one except her husband unless there is a dire necessity for doing so. Moreover, the spiral could cause a menstruation disorder which - in turn - may have an effect on many religious matters such as: prayer, fasting, purity, Hajj, touching the Musahaf and even the intimate relations with one's husband. The above rule concerns a woman who has not yet had it fixed.
As for the one who has already had it fixed, the rule depends on one of two situations:
First, It was fixed for a real necessity and it has not had any influence on the menstruation period, in this case the rule after it was fixed is the same as the rule before it was fixed. If it causes any disorder, then the blood that comes out can be considered as menstruation blood or an Istihadha (prolonged flow of blood outside the regular period) blood. Initially any blood that comes out of the woman's vagina is considered as menstruation blood and the rules concerning the woman, in that state are the same as the rules of the menstruating woman as long as this flow of blood does not exceed the longest period for a menstruation which the scholars defined as 15 days and as long as the state of this blood is similar to that of the menstruation blood after the normal period of the woman.
But, if it exceeds half a month or if its state changes from that of the menstruation blood, then the rule of a pure woman applies on her after having passed the normal period of a menstruating woman. She should then make her Ghusl (ritual wash), wear a protecting diaper. So, whenever the time of prayer comes, she should make her Wudu and pray. She should do this for every prayer.
The second situation is when the woman gets the spiral fixed in a time when she is not in a dire necessity. As we said earlier this is forbidden. But, if she has already done so and it does not effect the menstruation period in any way, then she can leave it. But, if it causes any disorder in the menstruation period, she should get rid of it. The rule in the second situation is different from the one in the first situation because in the first situation the woman was in dire necessity for the spiral and she is not responsible for any blood that comes due to this operation, as she cannot stop it. Whereas in the second situation this is not the case. The woman here had it fixed without real necessity to do so. She is then responsible for any consequences for this fixing.
Note also that if the woman can fix the spiral herself or if her husband can do it for her and if this does not cause disorder in the menstruation, we believe that it is lawful even if there is no particular necessity for that as it is in this case like Azal (husband not letting sperm go into his wife's vagina) which is lawful according the preponderant view of the scholars.
As for delaying pregnancy and enjoying wife in menstrual period please refer to fatawa: 81150, 81459, 81836.
Allah knows best.