The definition of a married Brahmachari is given in the following Yajnavalkya Smriti verse:
LXXIX.—Sixteen nights are the "" Season " of women. Among these he
should approach them during the even nights. Let him avoid the Parvana
nights, &c. and the first four nights. By so doing he would be even a
Brahmachari.—79
On this verse we have the following Mitakasra commentary:
That period of women, indicative of the state in which they are
capable of getting conception, is called *' Season." And that period
is " sixteen days and nights," counting from the first day of
menstruation. In *' such " a season, and during ** even" i.e., equal
(and not odd) nights, *' he should approach " or go to his wife for
the sake of begetting a son. By specifying "night" day-time has been
excluded. " Even nights," being in the plural number, indicates
totality taken separately as well as collectively. So that in one
season he may go in all even nights which have not been (otherwise)
prohibited. By so doing he is even " like a Brahmachari." Therefore,
when Brahmacharya (abstention from women) is ordained in Sraddha, &c.
then by going as above, he is not guilty of transgressing the rule of Brahmacharya.
From the above discussion it does not seem to me that having sex without the intention of begetting progeny will be counted as "Brahmacharya".